Eleven numbers are randomly chosen from the set of integers, `S`, where
`S = {1, 2, 3, 4, ..., 20}`
Prove that the sum of two of the eleven numbers randomly selected must equal 21. (2 marks)
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Eleven numbers are randomly chosen from the set of integers, `S`, where
`S = {1, 2, 3, 4, ..., 20}`
Prove that the sum of two of the eleven numbers randomly selected must equal 21. (2 marks)
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`text(Proof (Show Worked Solution))`
`text(Rearranging)\ S\ text(into 10 pairs that sum to 21:)`
`{1, 20}, {2, 19}, {3, 18}, …. , {10, 11}`
`text(Select one number from each pair)`
`=>\ text(10 numbers where two do not sum to 21`
`text(The 11th number chosen must complete a pair that sums to 21)`
`:. \ text(By PHP, two of the eleven numbers must sum to 21.)`
A multiple choice quiz asks students 4 questions. Each question has three possible answers, a, b or c, and students must attempt each question.
How many students must do the quiz to ensure that at least two sets of answers are identical? (2 marks)
`82`
`text(Total possible answer combinations)`
`= 3 xx 3 xx 3 xx 3`
`= 81`
`:. \ text(By PHP, 82 students must do the quiz. `
A paint company claims that the mean time taken for its paint to dry when motor vehicles are repaired is 3.55 hours, with a standard deviation of 0.66 hours.
Assume that the drying time for the paint follows a normal distribution and that the claimed standard deviation value is accurate.
Write down the mean and standard deviation of `barX`. (2 marks)
At a car crash repair centre, it was found that the mean time taken for the paint company's paint to dry on randomly selected vehicles was 3.85 hours. The management of this crash repair centre was not happy and believed that the claim regarding the mean time taken for the paint to dry was too low. To test the paint company's claim, a statistical test was carried out.
a. `E(barX)` | `= 3.55` |
`sigma(barX)` | `= (sigma)/(sqrtn)` |
`= (0.66)/(sqrt36)` | |
`= 0.11` |
b. `H_0 : \ mu = 3.55`
`H_1 : \ mu > 3.55`
c. `p` | `= text(Pr) (barX > 3.85)` |
`= text(Pr) (z > (3.85 – 3.55)/(0.11))` | |
`= text(Pr) (z >2.326)` | |
`= 0.003 \ text{(to 3 decimal places)}` |
d. `text(S) text(ince)\ \ p < 0.01 , H_0 \ text(should be rejected at the 1% level.)`
`text(i.e. repair centre is justified that the mean time 3.55 hours is too low.)`
e. `text(If) \ \ mu = 3.55`
`(barX – mu)/(sigma)` | `> 2.3263` |
`barX` | `> 2.3263 xx 0.11 + 3.55` |
`barX` | `> 3.806` |
f. `text(Pr) (barX< 3.806 | mu = 3.83)` | `= text(Pr) (z < (3.806 – 3.83)/(0.11))` |
`= text(Pr) (z < -0.21818)` | |
`= 0.41` |
A pallet of bricks weighing 500 kg sits on a rough plane inclined at an angle of `α°` to the horizontal, where `tan(α°) = (7)/(24)`. The pallet is connected by a light inextensible cable that passes over a smooth pulley to a hanging container of mass `m` kilograms in which there is 10 L of water. The pallet of bricks is held in equilibrium by the tension `T` newtons in the cable and a frictional resistance force of 50 `g` newtons acting up and parallel to the plane. Take the weight force exerted by 1 L of water to be `g` newtons.
Suddenly the water is completely emptied from the container and the pallet of bricks begins to slide down the plane. The frictional resistance force of 50 `g` newtons acting up the plane continues to act on the pallet.
a.
b. `text(Resolving vertical forces on container:)`
`T – (m + 10)g = 0 \ …\ (1)`
`text(Resolving forces on plane:)`
`tan α = (7)/(24) \ => \ sin α = (7)/(25)`
`text(Solve for m:)`
`(m + 10)g` | `= 500 text(g) · (7)/(25) – 50 text(g)` |
`m + 10` | `= 140 – 50` |
`:. \ m` | `= 80` |
c. `text(Resolving vertical forces on container:)`
`T – 80 g = 80 a \ …\ (1)`
`text(Resolving forces on plane:)`
`500 g sin α – (T + 50 g) = 500 a`
`90 g – T = 500 a \ …\ (2)`
`text(Add) \ (1) + (2)`
`10 g` | `= 580 a` |
`a` | `= (g)/(58)` |
`s` | `= ut + (1)/(2) at^2` |
`= 0 + (1)/(2) · (g)/(58) + 10^2` | |
`= (25g)/(29)` |
d.i. `m = 80 + 2t`
d.ii. `text(Resolving vertical forces on container:)`
`T – (80+2t)g = (80+2t)a \ …\ (1)`
`text(Resolving forces on plane:)`
`90g – T = 500a \ …\ (2)`
`text(Add)\ (1) + (2)`
`(90 – 80 – 2t)g` | `= (500 + 80 + 2t)a` |
`(10 – 2t)g` | `=(580 + 2t)a` |
`a` | `= (g(5 – t))/(t + 290) ms^-2` |
d.iii. `(dv)/(dt) = (g(5 – t))/(t + 290)`
`v = int (dv)/(dt)\ dt = 295 log_e ((t + 290)/(290)) – g t + c`
`text(When)\ t = 0, v = 3\ \ text{(given)} \ => \ c = 3`
`:. \ v = 295 log_e ((t+290)/(290)) – g t + 3`
`:. \ v(4) = 3.4\ text(ms)^-1`
The vertical cross-section of a barrel is shown above. The radius of the circular base (along the `x`-axis) is 30 cm and the radius of the circular top is 70 cm. The curved sides of the cross-section shown are parts of the parabola with rule `y = (x^2)/(80) - (45)/(4)`. The height of the barrel is 50 cm.
a. i. Show that the volume of the barrel is given by `pi int_0^50 (900 + 80 y)\ dy`. (1 marks)
ii. Find the volume of the barrel in cubic centimetres. (1 marks)
The barrel is initially full of water. Water begins to leak from the bottom of the barrel such that `(dV)/(dt) = (-8000pi sqrth)/(A)` cubic centimetres per second, where after `t` seconds the depth of the water is `h` centimetres, the volume of water remaining in the barrel is `V` cubic centimetres and the uppermost surface area of the water is `A` square centimetres.
b. Show that `(dV)/(dt) = (-400 sqrth)/(4h + 45)`? (2 marks)
c. Find `(dh)/(dt)` in terms of `h`. Express your answer in the form `(-a sqrth)/(pi(b + ch)^2)`, where `a, b` and `c` are positive integers. (3 marks)
d. Using a definite integral in terms of `h`, find the time, in hours, correct to one decimal place, taken for the barrel to empty. (2 marks)
a. i. `text(Proof(Show Worked Solution))`
ii. `145000 pi \ text(cm)^3`
b. `text(Proof (Show Worked Solution))`
c. `(-20 sqrth)/(pi(45 + 4h)^2)`
d. `9.9\ text(hours)`
a.i. | `V` | `= pi int x^2 dy` |
`y` | `= (x^2)/(80) – (45)/(4)` | |
`x^2` | `= 80y + 900` | |
`:. \ V` | `= pi int_0^50 (900 + 80y)dy` |
a.ii. | `V` | `= pi int_0_50 (900 + 80y) dy` |
`= pi [900y + 40y^2]_0^50` | ||
`= 145000pi \ text(cm)^3` |
b. `A = pi x^2 = pi (900 + 80h)`
`(dV)/(dt)` | `= (-8000pi sqrth)/(pi(900 + 80h))` |
`= (-8000 sqrth)/(20(4h + 45))` | |
`= (-400 sqrth)/(4h + 45)` |
c. `(dV)/(dh) = pi(900 + 80h)`
`(dh)/(dt)` | `= (dh)/(dV) ⋅ (dV)/(dt)` |
`= (1)/(pi(900 +80h)) xx (-400 sqrth)/(4h +45)` | |
`= (-400 sqrth)/(20pi(4h +45)^2)` | |
`= (-20 sqrth)/(pi(45 +4h)^2)` |
d. `(dt)/(dh) = (-pi(45 + 4h)^2)/(20 sqrth)`
`t` | `= -pi int_50^0 ((45 + 4h)^2)/(20 sqrth)\ dh` |
`≈ 35\ 598.6 \ text(seconds)` | |
`≈ 9.9 \ text{hours (to 1 d.p.)}` |
Consider the function `f` with rule `f(x) = (x^2 + x + 1)/(x^2-1)`.
Consider the function `f_k` with rule `f_k(x) = (x^2 + x + k)/(x^2-1)` where `k ∈ R`.
i. `f(x) = 1 + (x + 2)/((x + 1)(x-1))`
`:. \ text(Asymptotes at)\ \ x = 1, x = -1, y = 1`
ii. `f′(x) = (-(x^2 + 4x + 1))/(x^2-1)^2`
`text(Solve:) \ \ f^{′}(x) = 0 \ => \ x = -2 ± sqrt3`
`text(SP’s at) \ (-3.73, 0.87) \ \ text(and)\ \ (-0.27, -0.87)`
`f^{″}(x) = (-2x^3-12x^2-6x-4)/(x^2-1)^3`
`text(Solve:) \ \ f^{″}(x) = 0 \ => \ x = -5.52`
`text(POI at) \ \ (-5.52, 0.88)`
iii.
iv. `f_k^{′}(x) = (-x^2-2(k+1) x-1)/(x^2-1)^2`
`text(If no SP’s,) \ \ Δ < 0`
`[-2( k + 1)]^2-4(-1)(-1)` | `< 0` |
`4k^2 + 8k + 4-4` | `< 0` |
`4k(k + 2)` | `< 0` |
`:. \ -2 < k < 0`
v. `f_k^{″}(x) = (2(x^3 + 3(k + 1) x^2 + 3x + k + 1))/((x^2-1)^3)`
`text(Solve:)\ \ f_k^{″}(x) = 0`
`k = -1`
On average, batsmen playing cricket in a T20 competition play a scoring shot two out of every three balls.
In a regular season, a total of 1200 overs that each contain six balls, are bowled.
Estimate how many overs would have at least five scoring shots. (3 marks)
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`421`
`text(Let)\ \ X = text(number of scoring shots in a six ball over)`
`X\ ~\ text(Bin) (6, 2/3)`
`P(X >= 5)` | `= P(X = 5) + P(X = 6)` |
`=\ ^6 C_5 ⋅ (2/3)^5 (1/3) + \ ^6 C_6 ⋅ (2/3)^6` | |
`= 64/243 + 64/729` | |
`= 256/729` |
`text(Let)\ \ Y=\ text(number of overs with at least 5 scoring shots)`
`Y\ ~\ text(Bin)(1200, 256/729)`
`E(Y)` | `=np` | |
`=1200 xx 256/729` | ||
`=421.39…` | ||
`=421\ \ text{(nearest over)}` |
A manufacturer of pool cue tips knows that 4% of pool cue tips produced in its factory need to be scrapped.
A random sample of 10 cue tips produced in the factory is examined.
Give your answer correct to 3 decimal places. (1 mark)
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Give your answer correct to 3 decimal places. (2 marks)
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i. `text(Let)\ \ X = text(number of defective cue tips)`
`X\ ~\ text(Bi) (10, 0.04)`
`P(X = 3)` | `= \ ^10 C_3 ⋅ (0.04)^3 (0.96)^7` |
`= 0.00577…` | |
`=0.006\ \ text{(to 3 d.p.)}` |
ii. | `P(X <= 2)` | `= P(X = 0) + P(X = 1) + P(X = 2)` |
`=\ ^10 C_0(0.04)^0 (0.96)^10 + \ ^10 C_1(0.04) (0.96)^9 + \ ^10 C_2 (0.04)^2 (0.96)^8` | ||
`= 0.66483 + 0.27701 + 0.05194` | ||
`= 0.994\ \ text{(to 3 d.p.)}` |
A snowboarder at the Winter Olympics leaves a ski jump at an angle of `theta` degrees to the horizontal, rises up in the air, performs various tricks and then lands at a distance down a straight slope that makes an angle of 45° to the horizontal, as shown below.
Let the origin `O` of a cartesian coordinate system be at the point where the snowboarder leaves the jump, with a unit vector in the positive `x` direction being represented by `underset~i` and a unit vector in the positive `y` direction being represented by `underset~j`. Distances are measured in metres and time is measured in seconds.
The position vector of the snowboarder `t` seconds after leaving the jump is given by
`underset~r (t) = (6t - 0.01t^3) underset~i + (6 sqrt3 t - 4.9t^2 + 0.01t^3) underset~j , \ t ≥ 0`
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a. `v(t) = (6 – 0.03t^2)underset~i + (6 sqrt3 – 9.8t + 0.03t^2) underset~j`
`text(When) \ t =0,`
`v(t) = 6underset~i + 6 sqrt3 underset~j`
`tan theta = (6 sqrt3)/(6) = sqrt3`
`:. \ theta` | `= tan^-1 sqrt3` |
`= 60°` |
b. | `text(Speed)` | `= |v(0)|` |
`= sqrt(6^2 + (6 sqrt3)^2)` | ||
`= 12 \ text(ms)^-1` |
c. `text(Max height when) \ underset~j \ text(component of) \ v(t) = 0`
`text(Solve): \ \ 6 sqrt3 – 9.8t + 0.03t^2 = 0`
`=> t = 1.064 \ text(seconds)`
`text(Max height)` | `= 6 sqrt3 (1.064) – 4.9(1.064)^2 + 0.01(1.064)^3` | |
`~~5.5\ text(m)` |
d. `text(Time of Flight ⇒ Solve for)\ \ t\ \ text(when)\ \ y=-x:`
`6 sqrt 3 t – 4.9t^2 + 0.01 t^3` | `= -(6t-0.01t^3)` |
`(6 + 6 sqrt3)t – 4.9 t^2` | `= 0` |
`t(6 + 6 sqrt3 – 4.9 t)` | `= 0` |
`4.9 t` | `= 6 + 6 sqrt3` |
`t` | `= (6 + 6 sqrt3)/(4.9)` |
`= (60(sqrt3 + 1))/(49)\ text(seconds)` |
A snowboarder at the Winter Olympics leaves a ski jump at an angle of `theta` degrees to the horizontal, rises up in the air, performs various tricks and then lands at a distance down a straight slope that makes an angle of 45° to the horizontal, as shown below.
Let the origin `O` of a cartesian coordinate system be at the point where the snowboarder leaves the jump, with a unit vector in the positive `x` direction being represented by `underset~i` and a unit vector in the positive `y` direction being represented by `underset~j`. Distances are measured in metres and time is measured in seconds.
The position vector of the snowboarder `t` seconds after leaving the jump is given by
`underset~r (t) = (6t - 0.01t^3) underset~i + (6 sqrt3 t - 4.9t^2 + 0.01t^3) underset~j , \ t ≥ 0`
a. `v(t) = (6 – 0.03t^2)underset~i + (6 sqrt3 – 9.8t + 0.03t^2) underset~j`
`text(When) \ t =0,`
`v(t) = 6underset~i + 6 sqrt3 underset~j`
`tan theta = (6 sqrt3)/(6) = sqrt3`
`:. \ theta` | `= tan^-1 sqrt3` |
`= 60°` |
b. | `text(Speed)` | `= |v(0)|` |
`= sqrt(6^2 + (6 sqrt3)^2)` | ||
`= 12 \ text(ms)^-1` |
c. `text(Max height when) \ underset~j \ text(component of) \ v(t) = 0`
`text(Solve): \ \ 6 sqrt3 – 9.8t + 0.03t^2 = 0`
`=> t = 1.064 \ text(seconds)`
`text(Max height)` | `= 6 sqrt3 (1.064) – 4.9(1.064)^2 + 0.01(1.064)^3` | |
`~~5.5\ text(m)` |
d. `text(Time of Flight ⇒ Solve for)\ \ t\ \ text(when)\ \ y=-x:`
`6 sqrt 3 t – 4.9t^2 + 0.01 t^3` | `= -(6t-0.001t^3)` |
`(6 + 6 sqrt3)t – 4.9 t^2` | `= 0` |
`t(6 + 6 sqrt3 – 4.9 t)` | `= 0` |
`4.9 t` | `= 6 + 6 sqrt3` |
`t` | `= (6 + 6 sqrt3)/(4.9)` |
`= (60(sqrt3 + 1))/(49)\ text(seconds)` |
e. `text(Total distance) \ = text(Area under) \ v(t) \ text(graph from)\ \ t = 0 \ \ text(to)\ \ t_1 = (60(sqrt3 + 1))/(49)`
`|v(t)| = sqrt{(6 – 0.03 t^2)^2 + (6 sqrt3 – 9.8t + 0.03 t^2)^2}`
`text(Distance)` | `= int_0^(t_1) |v(t)| \ dt` |
`= 38.51 \ text{m (to 2 d.p.)}` |
In the complex plane, `L` is the with equation `|z + 2| = |z - 1 - sqrt3 i|`.
Find `z_1` in cartesian form. (2 marks)
a. `text(Substitute)\ \ z = 0 + 0i\ \ text(into both sides:)`
`text(LHS) = |2| = 2`
`text(RHS) = |-1 – sqrt3i| = sqrt{(-1)^2 + (-sqrt3)^2} = 2`
`:. (0,0)\ \ text(lies on both sides.)`
b. | `|x + yi + 2|` | `= |x + yi – 1 – sqrt3 i|` |
`|(x + 2) + yi|` | `= |(x – 1) + (y – sqrt3) i|` | |
`sqrt(x^2 + 4x + 4 + y^2` | `= sqrt(x^2 – 2x + 1 + y^2 -2 sqrt3 y + 3` | |
`x^2 + 4x + 4 + y^2` | `= x^2 – 2x + 4 – 2 sqrt3 y + y^2` | |
`6x` | `= -2 sqrt3 y` | |
`y` | `= -(3)/(sqrt3) x` | |
`y` | `= -sqrt3 x` |
c.
`m_text(perp) = (sqrt2)/(3) , text(through)\ (1, 0)`
`y = (sqrt3)/(3) (x – 1)\ …\ L_1`
`text(Intersection) \ L\ text(and) \ L_1,`
`text(Solve:) \ (sqrt3)/3 (x-1) = -sqrt3 x\ \ \ text{(by CAS)}`
`=> x = (1)/(4) , y = -(sqrt3)/(4) \ \ \ text{(point}\ Ptext{)}`
`P(x_1,y_1) \ text(is midpoint of) \ \ z_1 \ text(and) \ \ (1, 0):`
`(x_1 + 1)/(2) = (1)/(4) \ => \ x_1 = -(1)/(2)`
`(y_1 + 0)/(2) = -sqrt3/(4) \ => \ y_1 = -sqrt3/(2)`
`:. \ z_1 = -(1)/(2) – (sqrt3)/(2) i`
d. `|z| = 4 => \ text(circle, centre) \ (0,0), \ text(radius) = 4`
`x^2 + y^2 = 16\ …\ (1)`
`y = – sqrt3 x\ …\ (2)`
`text(Substitute)\ (2) \ text(into) \ (1)`
`x^2 + 3x^2 = 16`
`x = ±2`
`:. \ text(Intersection at)\ (2, – 2 sqrt3) \ text(and) \ (-2, 2 sqrt3)`
e.
f.
`text(Area)` | `= (5)/(12) xx pi xx 4^2` |
`= (20pi)/(3)` |
Consider a random variable `X` with probability density function
`f(x) = {(2x,, 0<= x <= 1),(0,, x < 0\ \ text(or)\ \ x > 1):}`
If a large number of samples, each of size 100, is taken from his distribution, then the distribution of the sample means, `barX`, will be approximately normal with mean `E(barX) = 2/3` and standard deviation `text(sd)(barX)` equal to
`A`
`E(X) = E(barX) = 2/3`
`E(X^2) = int_0^1 x^2 · 2x\ dx = [(x^4)/2]_0^1 = 1/2`
`text(Var)(X)` | `= E(X^2)-[E(X)]^2` |
`= 1/2-4/9` | |
`= 1/18` |
`sigma(barX) = (sqrt(1/18))/sqrt100 = 1/(10 xx 3sqrt2) = sqrt2/60`
`=>\ A`
The position vector `underset~r(t)` of a mass of 3 kg after `t` seconds, where `t >= 0`, is given by `underset~r(t) = 10tunderset~i + (16t^2 - 4/3t^3)underset~j`.
The force, in newtons, acting on the mass when `t = 2` seconds is
`C`
`underset~r(t) = 10tunderset~i + (16t^2 – 4/3t^3)underset~j`
`underset~v(t) = 10underset~i + (32t – 4t^2)underset~j`
`underset~a(t) = (32 – 8t)underset~j`
`text(When)\ t = 2,`
`underset~F` | `= m underset~a` |
`= 3(32 – 16)underset~j` | |
`= 48underset~j` |
`=>\ C`
For the vectors `underset~a = underset~i + 3underset~j - underset~k`, `underset~b = −underset~i - 4underset~j + 2underset~k` and `underset~c = −underset~i - 6underset~j + lambdaunderset~k` to be linearly dependent, the value of `lambda` must be
`E`
`text(Linearly dependent if)\ ∃ lambda, m, n,\ text(such that)`
`((−1),(−6),(lambda)) = m((1),(3),(−1)) + n((−1),(−4),(2))`
`text{Solve (by CAS):}`
`lambda = 4, m = 2, n = 3`
`=>\ E`
The acute angle `theta` is the angle between the vectors `underset~a = −2underset~i + 2underset~j - underset~k` and `underset~b = −4underset~i + 4underset~j + 7underset~k`.
Find the exact value of `sin(2theta)`. (2 marks)
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`(4sqrt2)/9`
`underset~a = ((−2),(2),(−1)), \ |underset~a| = sqrt(4 + 4 + 1) = 3`
`underset~b = ((−4),(4),(7)), \ |underset~b| = sqrt(16 + 16 + 49) = 9`
`underset~a · underset~b = ((−2),(2),(−1))((−4),(4),(7)) = 8 + 8 – 7 = 9`
`costheta = (underset~a · underset~b)/(|underset~a||underset~b|) = 9/(3 xx 9) = 1/3`
`sintheta` | `= sqrt8/3` |
`sin2theta` | `= 2sinthetacostheta` |
`= 2 · sqrt8/3 · 1/3` | |
`= (4sqrt2)/9` |
Given that `theta` is the acute angle between the vectors `underset~a = −2underset~i + 2underset~j - underset~k` and `underset~b = −4underset~i + 4underset~j + 7underset~k`, then `sin(2theta)` is equal to
`B`
`underset~a = ((−2),(2),(−1)), \ |underset~a| = sqrt(4 + 4 + 1) = 3`
`underset~b = ((−4),(4),(7)), \ |underset~b| = sqrt(16 + 16 + 49) = 9`
`underset~a · underset~b = ((−2),(2),(−1))((−4),(4),(7)) = 8 + 8 – 7 = 9`
`costheta = (underset~a · underset~b)/(|underset~a||underset~b|) = 9/(3 xx 9) = 1/3`
`sintheta` | `= sqrt8/3` |
`sin2theta` | `= 2sinthetacostheta` |
`= 2 · sqrt8/3 · 1/3` | |
`= (4sqrt2)/9` |
`=>\ B`
The vector resolute of `underset~a = 2underset~i - underset~j + 3underset~k` that is perpendicular to `underset~b = underset~i + underset~j - underset~k` is
`C`
`underset~a = ((2),(−1),(3)),\ \ underset~b = ((1),(1),(−1))`
`|underset~b| = sqrt3`
`underset~a · underset~b = 2 – 1 – 3 = −2`
`text(Vector resolute)\ underset~a\ text(onto)\ underset~b`
`= (underset~a · underset~overset^b)underset~overset^b`
`= −2/sqrt3 xx 1/sqrt3((1),(1),(−1))`
`= −2/3((1),(1),(−1))`
`text(Vector resolute)\ underset~a ⊥ underset~b`
`= underset~a – (underset~a · underset~overset^b)underset~overset^b`
`= ((2),(−1),(3)) + 2/3((1),(1),(−1))`
`= 1/3((8),(−1),(7))`
`=>\ C`
Euler's method, with a step size of 0.1, is used to approximate the solution of the differential equation `1/y(dy)/(dx) = cos(x)`, with `y = 2` when `x = 0`.
When `x = 0.2`, the value obtained for `y`, correct to four decimal places, is
`D`
`1/y · (dy)/(dx)` | `= cosx` |
`(dy)/(dx)` | `= ycosx` |
`text(Using)\ \ y_0 = 2, x_0 = 0, h = 0.1:`
`y_1` | `= y_0 + h(y_0cosx_0)` |
`= 2 + 0.1(2cos0)` | |
`= 2.2` |
`y_2` | `= 2.2 + 0.1(2.2cos(0.1))` |
`= 2.4189` |
`=>\ D`
With a suitable substitution, `int_1^2sqrt(5x - 1)\ dx` can be expressed as
`D`
`text(Let)\ \ u = 5x – 1`
`(du)/(dx) = 5\ \ =>\ 1/5\ du = dx`
`text(When)\ \ x = 2, u = 9`
`text(When)\ \ x = 1, u = 4`
`int_1^2sqrt(5x – 1)\ dx = 1/5 int_4^9 sqrtu\ du`
`=>\ D`
The total area enclosed between the `x`-axis and the graph of `f(x) = |x^3| - x^2 - |x|` is closest to
`D`
`text(Graph)\ \ f(x) = |x^3| – x^2 – |x|\ \ \ (text(by CAS))`
`text(Intersection occurs at:)`
`x = 0, ±((1 + sqrt5)/2)`
`=>\ text(Function is even)`
`:.\ text(Area)` | `= −2int_0^(1 + sqrt5) f(x)\ dx\ \ (text(area is below axis))` |
`= 2.015` |
`=>\ D`
The gradient of the line that is perpendicular to the graph of a relation at any point `P(x, y)` is half the gradient of the line joining `P` and the point `Q(−1,1)`.
The relation satisfies the differential equation
`E`
`m_(PQ) = (y – 1)/(x + 1) \ => \ m_text(perp) = 1/2((y – 1)/(x + 1))`
`:. m_text(perp) · (dy)/(dx)` | `= −1` |
`1/2((y – 1)/(x + 1))(dy)/(dx)` | `= −1` |
`(dy)/(dx)` | `= −2 ((x + 1)/(y – 1))` |
`= (2(x + 1))/(1 – y)` |
`=>\ E`
Which one of the following statements is false for `z_1, z_2 ∈ C`?
`B`
The maximal domain and range of the function `f(x) = acos^(−1)(bx) + c`, where `a`, `b` and `c` are real constants with `a > 0`, `b < 0` and `c > 0`, are respectively
`D`
`text(Domain:)\ ` | `−1 <= bx <= 1, \ \ b < 0` |
`1/b <= x <= −1/b` |
`text(Range:)\ ` | `0 <= cos^(−1)(bx) <= pi` |
`0 <= acos^(−1)(bx) <= api` | |
`c <= acos^(−1)(bx) + c <= api + c` |
`=>\ D`
A circle with centre `(a,−2)` and radius 5 units has equation
`x^2-6x + y^2 + 4y = b` where `a` and `b` are real constants.
The values of `a` and `b` are respectively
A. −3 and 38
B. 3 and 12
C. −3 and −8
D. 3 and 18
`B`
`x^2-6x + y^2 + 4y=b`
`text(Completing the squares:)`
`x^2-6x + 3^2-9 + y^2 + 4y + 2^2-4` | `= b` |
`(x-3)^2 + (y + 2)^2-13` | `= b` |
`(x-3)^2 + (y + 2)^2` | `= b + 13` |
`:. a=3`
`:. b+13=25\ \ =>\ \ b=12`
`=> B`
The curve given by `x = 3sec(t) + 1` and `y = 2tan(t) - 1` can be expressed in cartesian form as
`E`
`sec^2theta = tan^2theta + 1`
`x = 3sec(t) + 1 \ => \ sec(t) = (x – 1)/3`
`y = 2tan(t) – 1 \ => \ tan(t) = (y + 1)/2`
`:.((x – 1)/3)^2 – ((y + 1)/2)^2` | `= 1` |
`((x – 1)^2)/9 – ((y + 1)^2)/4` | `= 1` |
`=>\ E`
A projectile is fired from a canon at ground level with initial velocity `sqrt300` ms−1 at an angle of 30° to the horizontal.
The equations of motion are `(d^2x)/(dt^2) = 0` and `(d^2y)/(dt^2) = −10`.
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i.
`dotx = sqrt300\ cos30^@ = 10sqrt3 xx sqrt3/2 = 15\ text(ms)^(−1)`
`x = int 15\ dt = 15t + C_1`
`text(When)\ \ t = 0, \ x = 0 \ => \ C_1 = 0`
`:. x = 15t`
ii. `doty = int −10\ dt = −10t + C_1`
`text(When)\ \ t = 0, \ doty = 10sqrt3 sin30^@ = 5sqrt3 \ => \ C_1 = 5sqrt3`
`:. doty = 5sqrt3 – 10t`
`y = int doty\ dt = 5sqrt3t – 5t^2 + C_2`
`text(When)\ \ t = 0, \ y = 0 \ => \ C_2 = 0`
`:. y = 5sqrt3t – 5t^2`
iii. `x = 15t \ => \ t = x/15`
`y` | `= 5sqrt3 xx x/15 – 5(x/15)^2` | |
`:.y` | `=sqrt3/3 x – (x^2)/45` |
By using the fact that `(1 + x)^11 = (1 + x)^3(1 + x)^8`, show that
`((11),(5)) = ((8),(5)) + ((3),(1))((8),(4)) + ((3),(2))((8),(3)) + ((8),(2))`. (3 marks)
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`text(See Worked Solutions)`
`text(General term of)\ \ (1 + x)^11 :`
`T_k = \ ^11C_k · 1^(11 – k) · x^k`
`=> \ ^11C_5\ text(is the co-efficient of)\ x^5`
`(1 + x)^3 = \ ^3C_0 + \ ^3C_1 x + \ ^3C_2 x^2 + \ ^3C_3 x^3`
`(1 + x)^8 = \ ^8C_0 + \ ^8C_1 x + \ ^8C_2 x^2 + \ ^8C_3 x^3 + \ ^8C_4 x^4 + \ ^8C_5 x^5 + …`
`:.\ text(Coefficient of)\ x^5\ text(in)\ \ (1 + x)^3(1 + x)^8 `
`= \ ^3C_0 · \ ^8C_5 + \ ^3C_1 · \ ^8C_4 + \ ^3C_2 · \ ^8C_3 + \ ^3C_3 · \ ^8C_2`
`= \ ^8C_5 + \ ^3C_1 · \ ^8C_4 + \ ^3C_2 · \ ^8C_3 + \ ^8C_2`
`text(Equating coefficients:)`
`((11),(5)) = ((8),(5)) + ((3),(1))((8),(4)) + ((3),(2))((8),(3)) + ((8),(2))`
Show `\ ^nC_k = \ ^(n-1)C_(k-1) + \ ^(n-1)C_k`. (2 marks)
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`text(See Worked Solutions)`
`text(LHS) = (n!)/((n-k)!k!)`
`text(RHS)` | `= ((n-1)!)/((n-1-(k-1))!(k-1)!) + ((n-1)!)/((n-1-k)!k!)` |
`= ((n-1)!k)/((n-k)!(k-1)!k) + ((n-1)!(n-k))/((n-k-1)!(n-k)k!)` | |
`= ((n-1)!k)/((n-k)!k!) + ((n-1)!(n-k))/((n-k)!k!)` | |
`= ((n-1)!(k + n-k))/((n-k)!k!)` | |
`= (n!)/((n-k)!k!)` | |
`=\ text(LHS)` |
i. Show that `tan((5pi)/(12)) = sqrt3 + 2`. (2 marks)
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ii.
Hence, find the area bounded by the graph of `f(x) = (2)/(x^2 - 4x + 8)` shown above, the `x`-axis and the lines `x = 0` and `x = 2 sqrt3 +6`. (4 marks)
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i. `text(Method 1:)`
`tan \ (5pi)/(12)` | `= tan ((pi)/(4) + (pi)/(6))` |
`= (tan \ (pi)/(4) + tan\ (pi)/(6))/(1 – tan \ (pi)/(4) · tan \ (pi)/(6))` | |
`= (1 + (1)/(sqrt3))/(1 – (1)/(sqrt3))` | |
`= (sqrt3+1)/(sqrt3-1) xx (sqrt3+1)/(sqrt3+1)` | |
`= (3+ 2 sqrt3 + 1)/(3 – 1)` | |
`= sqrt3 +2` |
`text(Method 2:)`
`tan \ (5pi)/(6)` | `= (2tan \ (5pi)/(12))/(1 – tan^2 \ (5pi)/(12))` |
`- 1/sqrt3` | `=(2tan \ (5pi)/(12))/(1 – tan^2 \ (5pi)/(12))` |
`-2 sqrt3 tan \ (5pi)/(12)` | `= 1 – tan^2 \ (5pi)/(12)` |
`tan^2 \ (5pi)/(12) – 2 sqrt(3) tan \ (5pi)/(12) – 1 = 0`
`tan \ (5pi)/(12)` | `= (2 sqrt3 ± sqrt(12 + 4))/(2)` |
`= sqrt3 + 2 \ \ \ (tan theta > 0)` |
ii. `text(Area)` | `= int_0 ^(2 sqrt3 + 6) \ (2)/(x^2 – 4x + 8)\ dx` |
`= int_0 ^(2 sqrt3 + 6) \ (2)/((x -2)^2 + 2^2)` | |
`= [tan^-1 ((x – 2)/(2))]_0 ^(2 sqrt3 + 6)` | |
`= tan^-1 (sqrt3 + 2) – tan^-1 (-1)` | |
`= (5pi)/(12) – (-(pi)/(4))` | |
`= (2pi)/(3)` |
a. `text(Method 1:)`
`tan \ (5pi)/(12)` | `= tan ((pi)/(4) + (pi)/(6))` |
`= (tan \ (pi)/(4) + tan\ (pi)/(6))/(1 – tan \ (pi)/(4) · tan \ (pi)/(6))` | |
`= (1 + (1)/(sqrt3))/(1 – (1)/(sqrt3))` | |
`= (sqrt3+1)/(sqrt3-1) xx (sqrt3+1)/(sqrt3+1)` | |
`= (3+ 2 sqrt3 + 1)/(3 – 1)` | |
`= sqrt3 +2` |
`text(Method 2:)`
`tan \ (5pi)/(6)` | `= (2tan \ (5pi)/(12))/(1 – tan^2 \ (5pi)/(12))` |
`- 1/sqrt3` | `=(2tan \ (5pi)/(12))/(1 – tan^2 \ (5pi)/(12))` |
`-2 sqrt3 tan \ (5pi)/(12)` | `= 1 – tan^2 \ (5pi)/(12)` |
`tan^2 \ (5pi)/(12) – 2 sqrt(3) tan \ (5pi)/(12) – 1 = 0`
`tan \ (5pi)/(12)` | `= (2 sqrt3 ± sqrt(12 + 4))/(2)` |
`= sqrt3 + 2 \ \ \ (tan theta > 0)` |
b. `text(Area)` | `= int_0 ^(2 sqrt3 + 6) \ (2)/(x^2 – 4x + 8)\ dx` |
`= int_0 ^(2 sqrt3 + 6) \ (2)/((x -2)^2 + 2^2)` | |
`= [tan^-1 ((x – 2)/(2))]_0 ^(2 sqrt3 + 6)` | |
`= tan^-1 (sqrt3 + 2) – tan^-1 (-1)` | |
`= (5pi)/(12) – (-(pi)/(4))` | |
`= (2pi)/(3)` |
Find the length of the arc of the curve defined by `y = (x^4)/(4) + (1)/(8x^2) + 3` from `x = 1` to `x = 2`. Give your answer in the form `(a)/(b)`, where `a` and `b` are positive integers. (4 marks)
`(123)/(32)`
`(dy)/(dx) = x^3 + ((-2)/(8) x^-3) = x^3 – (1)/(4x^3)`
`1 + ((dy)/(dx))^2` | `= 1 + (x^6 – (1)/(2) + (1)/(16x^6))` |
`= (16x^6 + 16x^12 – 8x^6 + 1)/(16x^6)` | |
`= (16x^12 + 8x^6 + 1)/(16x^6)` | |
`= ((4x^6 + 1)^2)/(16x^6)` |
`text(Arc Length)` | `= int_1 ^2 sqrt(((4x^6 + 1)^2)/(16x^6))\ dx` |
`= int_1 ^2 (4x^6 + 1)/(4x^3)\ dx` | |
`= int_1 ^2 x^3 + (1)/(4x^3)\ dx` | |
`= [(x^4)/(4) – (1)/(8x^2)]_1 ^2` | |
`= [4 – (1)/(32) – ((1)/(4) – (1)/(8))]` | |
`= (123)/(32)` |
Given that `3x^2 + 2xy + y^2 = 6`, find `(d^2 y)/(dx^2)` at the point (1, 1). (5 marks)
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`- (3)/(2)`
`6x + 2y + 2x · (dy)/(dx) + 2y · (dy)/(dx)` | `= 0` |
`(2x + 2y) (dy)/(dx)` | `= -6x – 2y` |
`(dy)/(dx)` | `= (-6x – 2y)/(2x + 2y)` |
`6 + 2 (dy)/(dx) + 2 (dy)/(dx) + 2x *(d^2y)/dx^2 + 2 ((dy)/(dx))^2 + 2y · (d^2 y)/(dx^2) = 0`
`(2x + 2y) (d^2 y)/(dx^2) + 4 (dy)/(dx) + 2 ((dy)/(dx))^2 + 6 = 0`
`text(At) \ (1, 1):`
`4 (d^2 y)/(dx^2) + 4 ((-6 -2)/(2+2)) + 2 ((-6 -2)/(2 + 2))^2 + 6 ` | `= 0` |
`4 (d^2 y)/(dx^2) – 8 + 8 + 6` | `= 0` |
`(d^2 y)/(dx^2)` | `= – (3)/(2)` |
Part of the graph of `y = (2)/(sqrt(x^2-4x+3))`, where `x > 3`, is shown below.
Find the volume of the solid of revolution formed when the graph of `y = (2)/(sqrt(x^2-4x+3))` from `x = 4` to `x = 6` is rotated about the `x`-axis. Give your answer in the form `a log_e(b)` where `a` and `b` are real numbers. (5 marks)
`pi log_e ((9)/(5))`
`V = pi int_4 ^6 (4)/(x^2 – 4x + 3)\ dx`
`text(Using partial fractions:)`
`(4)/(x^2 – 4x + 3) = (a)/((x-3)) + (b)/((x-1))`
`a(x -1) + b(x – 3)= 4`
`text(When)\ \ x = 1, \ -2b = 4 => \ b = -2`
`text(When)\ \ x = 3, \ 2a = 4 => \ a = 2`
`:. \ V` | `= pi int_4 ^6 (2)/(x-3) – (2)/(x-1)\ dx` |
`= 2 pi [log_e(x-3) -log_e(x-1)]_4 ^6` | |
`= 2 pi [log_e 3 – log_e 5 – (log_e 1 – log_e3)]` | |
`= 2 pi (2log_e 3 – log_e 5)` | |
`= 2pi log_e((9)/(5))` |
The base of a pyramid is the parallelogram `ABCD` with vertices at points `A(2,−1,3), B(4,−2,1), C(a,b,c)` and `D(4,3,−1)`. The apex (top) of the pyramid is located at `P(4,−4,9)`.
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i. | `overset(->)(AB)` | `= (4 – 2)underset~i + (−2 + 1)underset~j + (1 – 3)underset~k` |
`= 2underset~i – underset~j – 2underset~k` |
`text(S)text(ince)\ ABCD\ text(is a parallelogram)\ => \ overset(->)(AB)= overset(->)(DC)`
`overset(->)(DC) = (a – 4)underset~i + (b – 3)underset~j + (c + 1)underset~k`
`a – 4 = 2 \ => \ a = 6`
`b – 3 = −1 \ => \ b = 2`
`c + 1 = −2 \ => \ c = −3`
ii. `overset(->)(AB) = 2underset~i – underset~j – 2underset~k`
`overset(->)(AD) = 2underset~i + 4underset~j – 4underset~k`
`cos angleBAD` | `= (overset(->)(AB) · overset(->)(AD))/(|overset(->)(AB)| · |overset(->)(AD)|)` |
`= (4 – 4 + 8)/(sqrt(4 + 1 + 4) · sqrt(4 + 16 + 16))` | |
`= 4/9` |
iii. | `1/2 xx text(Area)_(ABCD)` | `= 1/2 ab sin c` |
`text(Area)_(ABCD)` | `= |overset(->)(AB)| · |overset(->)(AD)| *sin(cos^(−1)\ 4/9)` |
`:. text(Area)_(ABCD)` | `= 3 · 6 · sqrt65/9` |
`= 2sqrt65\ text(u²)` |
A triangle has vertices `A(sqrt3 + 1, –2, 4), \ B(1, –2, 3)` and `C(2, –2, sqrt3 + 3)`.
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i. `overset(->)(BA) = ((sqrt3 + 1), (-2), (4)) – ((1), (-2), (3)) = ((sqrt3), (0), (1))`
`overset(->)(BC) = ((2), (-2), (sqrt3 + 3)) – ((1), (-2), (3)) = ((1), (0), (sqrt3))`
`cos ∠ABC` | `= (overset(->)(BA) · overset(->)(BC))/ (|overset(->)(BA)| |overset(->)(BC)|` |
`= (2 sqrt3)/(sqrt4 sqrt4)` | |
`= (sqrt3)/(2)` |
`:. \ ∠ABC = (pi)/(6)`
ii. | `text(Area)` | `= (1)/(2) · |overset(->)(BA)| |overset(->)(BC)| \ sin ∠ABC` |
`= (1)/(2) xx 2 xx 2 xx sin \ (pi)/(6)` | ||
`= 1 \ text(u²)` |
A triangle has vertices `A(sqrt3 + 1, –2, 4), \ B(1, –2, 3)` and `C(2, –2, sqrt3 + 3)`.
a. `overset(->)(BA) = ((sqrt3 + 1), (-2), (4)) – ((1), (-2), (3)) = ((sqrt3), (0), (1))`
`overset(->)(BC) = ((2), (-2), (sqrt3 + 3)) – ((1), (-2), (3)) = ((1), (0), (sqrt3))`
`cos ∠ABC` | `= (overset(->)(BA) · overset(->)(BC))/ (|overset(->)(BA)| |overset(->)(BC)|` |
`= (2 sqrt3)/(sqrt4 sqrt4)` | |
`= (sqrt3)/(2)` |
`:. \ ∠ABC = (pi)/(6)`
b. | `text(Area)` | `= (1)/(2) · |overset(->)(BA)| |overset(->)(BC)| \ sin ∠ABC` |
`= (1)/(2) xx 2 xx 2 xx sin \ (pi)/(6)` | ||
`= 1 \ text(u²)` |
Evaluate `int_(e^3) ^(e^4) (1)/(x log_e (x))\ dx`. (3 marks)
`log_e ((4)/(3))`
`text(Let)\ \ u = log_e x`
`(du)/(dx) = (1)/(x) \ => \ du = (1)/(x) dx`
`text(When) \ \ x = e^4 \ => \ u = 4`
`text(When) \ \ x = e^3 \ => \ u = 3`
`int_(e^3) ^(e^4) (1)/(x log_e (x))` | `= int_3 ^4 (1)/(u)\ du` |
`= [ log_e u]_3 ^4` | |
`= log_e 4 – log_e 3` | |
`= log_e ((4)/(3))` |
The number of cars per day making a U-turn at a particular location is known to be normally distributed with a standard deviation of 17.5. In a sample of 25 randomly selected days, a total of 1450 cars were observed making the U-turn.
Find an approximation, correct to two decimal places, for the probability that on 25 randomly selected days the average number of U-turns is less than 53. (1 mark)
a. `barx = (1450)/(25) = 58`
`(σ)/(sqrtn) = (17.5)/(sqrt25) = (35)/(2xx5) = (7)/(2)`
`text(Limit:)\ ` | `(58 – 2 xx (7)/(2) \ , \ 58 + 2 xx (7)/(2)) ` |
`= (51, 65)` |
b. `μ = 60 \ , \ (σ)/(sqrtn) = (7)/(2)`
`\ barX ∼ N (60, ((7)/(2))^2)`
`text(Pr) (barX < 53)` | `= text(Pr) (z <–2)` |
`= (0.05)/(2)` | |
`= 0.025` | |
`≈ 0.02 \ \ text{(round down)}` |
`text{(0.03 was also accepted as a correct answer)}`
A cubic polynomial has the form `p(z) = z^3 + bz^2 + cz + d, \ z ∈ C`, where `b, c, d ∈ R`.
Given that a solution of `p(z) = 0` is `z_1 = 3 - 2i` and that `p(–2) = 0`, find the values of `b, c` and `d`. (4 marks)
`b =-4 \ , \ c = 1 \ , \ d = 26`
`text(Roots:)\ \ z_1 = 3 – 2i \ , \ z_2 = 3 + 2i \ , \ z_3 = -2`
`p(z)` | `= (z – 3 + 2i )(z – 3 – 2i )(z + 2)` |
`= ((z-3)^2 – (2i)^2)(z+2)` | |
`= (z^2 – 6z + 9 + 4)(z + 2)` | |
`= (z^2 – 6z + 13)(z + 2)` | |
`= z^3 + 2z^2 – 6z^2 – 12z + 13z + 26` | |
`= z^3 – 4z^2 + z + 26` |
`:. \ b =-4 \ , \ c = 1 \ , \ d = 26`
A cubic polynomial has the form `p(z) = z^3 + bz^2 + cz + d, \ z ∈ C`, where `b, c, d ∈ R`.
Given that a solution of `p(z) = 0` is `z_1 = 3 - 2i` and that `p(–2) = 0`, find the values of `b, c` and `d`. (4 marks)
`b =-4 \ , \ c = 1 \ , \ d = 26`
`text(Roots:)\ \ z_1 = 3 – 2i \ , \ z_2 = 3 + 2i \ , \ z_3 = -2`
`p(z)` | `= (z – 3 + 2i )(z – 3 – 2i )(z + 2)` |
`= ((z-3)^2 – (2i)^2)(z+2)` | |
`= (z^2 – 6z + 9 + 4)(z + 2)` | |
`= (z^2 – 6z + 13)(z + 2)` | |
`= z^3 + 2z^2 – 6z^2 – 12z + 13z + 26` | |
`= z^3 – 4z^2 + z + 26` |
`:. \ b =-4 \ , \ c = 1 \ , \ d = 26`
A 10 kg mass is placed on a rough plane that inclined at 30° to the horizontal, as shown in the diagram below. A force of 40 N is applied to the mass up the slope and parallel to the slope. There is also a frictional resistance force of magnitude `F` that opposes the motion of the mass.
a.
`40 + F` | `= 10g sin30°` |
`F` | `= 98 xx 0.5 – 40` |
`= 9\ text(N)` |
b. `text(Frictional force)\ F\ text(acts down slope)`
`40 + P` | `= 10g sin30° + F` |
`P` | `= 5g + F – 40` |
`= 49 + 9 – 40` | |
`= 18\ text(N)` |
Evaluate `int_0^3 (8x)/(1 + x^2) \ dx`. (3 marks)
`4 log_e 10`
`int_0^3 (8x)/(1 + x^2) \ dx`
`= 4 int_0^3 (2x)/(1 + x^2) \ dx`
`= 4 [log_e (1 + x^2)]_0^3`
`= 4 [log_e (1 + 9) – log_e (1 + 0)]`
`= 4 [log_e 10 – log_e 1]`
`= 4 log_e 10`
Find `int x/(x^2-3)\ dx`. (2 marks)
`1/2 ln (x^2 – 3) + C`
`int x/(x^2 – 3)\ dx` | `= 1/2 int (2x)/(x^2 – 3)\ dx` | |
`= 1/2 ln (x^2 – 3) + C` |
Differentiate with respect to `x`:
`log_e x^x`. (2 marks)
`1 + log_ex`
`y` | `=log_e x^x` | |
`=xlog_ex` | ||
`dy/dx` | `=x*1/x + log_ex` | |
`=1 + log_ex` |
Differentiate `5^(x^2)5x`. (2 marks)
`5^(x^2 + 1)(ln5*2x^2 + 1)`
`y` | `= 5^(x^2) * 5x` |
`(dy)/(dx)` | `= ln5*2x*5^(x^2)*5x + 5^(x^2)*5` |
`=5^(x^2)(ln5*10x^2 + 5)` | |
`=5^(x^2 + 1)(ln5*2x^2 + 1)` |
A ship sails 6 km from `A` to `B` on a bearing of 121°. It then sails 9 km to `C`. The
size of angle `ABC` is 114°.
Copy the diagram into your writing booklet and show all the information on it.
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i. |
`text(Let point)\ D\ text(be due North of point)\ B`
`/_ABD` | `=180-121\ text{(cointerior with}\ \ /_A text{)}` |
`=59^@` | |
`/_DBC` | `=114-59` |
`=55^@` |
`:. text(Bearing of)\ \ C\ \ text(from)\ \ B\ \ text(is)\ 055^@`
ii. `text(Using cosine rule:)`
`AC^2` | `=AB^2+BC^2-2xxABxxBCxxcos/_ABC` |
`=6^2+9^2-2xx6xx9xxcos114^@` | |
`=160.9275…` | |
`:.AC` | `=12.685…\ \ \ text{(Noting}\ AC>0 text{)}` |
`=13\ text(km)\ text{(nearest km)}` |
iii. `text(Need to find)\ /_ACB\ \ \ text{(see diagram)}`
`cos/_ACB` | `=(AC^2+BC^2-AB^2)/(2xxACxxBC)` |
`=((12.685…)^2+9^2-6^2)/(2xx(12.685..)xx9)` | |
`=0.9018…` | |
`/_ACB` | `=25.6^@\ text{(to 1 d.p.)}` |
`text(From diagram,)`
`/_BCE=55^@\ text{(alternate angle,}\ DB\ text(||)\ CE text{)}`
`:.\ text(Bearing of)\ A\ text(from)\ C`
`=180+55+25.6` | |
`=260.6` | |
`=261^@\ text{(nearest degree)}` |
The bearing of `C` from `A` is 250° and the distance of `C` from `A` is 36 km.
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i. `text(There is 360)^@\ text(about point)\ A`
`:.theta + 250^@` | `= 360^@` |
`theta` | `= 110^@` |
ii. |
`a^2` | `= b^2 + c^2 − 2ab\ cos\ A` |
`CB^2` | `= 36^2 + 15^2 − 2 xx 36 xx 15 xx cos\ 110^@` |
`= 1296 + 225 −(text(−369.38…))` | |
`= 1890.38…` | |
`:.CB` | `= 43.47…` |
`= 43\ text{km (nearest km)}` |
The diagram shows information about the locations of towns `A`, `B` and `Q`.
Calculate her walking speed correct to the nearest km/h. (1 mark)
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Find the distance from Town `A` to Town `B`. Give your answer to the nearest km. (2 marks)
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i. `text(2 hrs 48 mins) = 168\ text(mins)`
`text(Speed)\ text{(} A\ text(to)\ Q text{)}` | `= 15/168` |
`= 0.0892…\ text(km/min)` |
`text(Speed)\ text{(in km/hr)}` | `= 0.0892… xx 60` |
`= 5.357…\ text(km/hr)` | |
`= 5\ text(km/hr)\ text{(nearest km/hr)}` |
ii. |
`text(Using cosine rule)`
`AB^2` | `= 15^2 + 10^2 – 2 xx 15 xx 10 xx cos 87^@` |
`= 309.299…` | |
`AB` | `= 17.586…` |
`= 18\ text(km)\ text{(nearest km)}` |
`:.\ text(The distance from Town)\ A\ text(to Town)\ B\ text(is 18 km.)`
iii. |
`/_CAQ` | `= 31^@\ \ \ text{(} text(straight angle at)\ A text{)}` |
`/_AQD` | `= 31^@\ \ \ text{(} text(alternate angle)\ AC\ text(||)\ DQ text{)}` |
`/_DQB` | `= 87 – 31 = 56^@` |
`/_QBE` | `= 56^@\ \ \ text{(} text(alternate angle)\ DQ \ text(||)\ BE text{)}` |
`:.\ text(Bearing of)\ Q\ text(from)\ B`
`= 180 + 56`
`= 236^@`
`OABC` is a quadrilateral.
`P`, `Q`, `R` and `S` divide each side of the quadrilateral in half as shown below.
Prove, using vectors, that `PQRS` is a parallelogram. (3 marks)
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`text(See Worked Solution)`
`text(Consider diagonal)\ \ overset(->)(OB):`
`overset(->)(OB) = overset(->)(OA) + overset(->)(AB) = overset(->)(OC)+ overset(->)(CB)`
`overset(->)(PQ) = overset(->)(PA) + overset(->)(AQ) = 1/2(overset(->)(OA) + overset(->)(AB)) = 1/2overset(->)(OB)`
`overset(->)(SR) = overset(->)(SC) + overset(->)(CR) = 1/2(overset(->)(OC) + overset(->)(CB)) = 1/2overset(->)(OB)`
`:.overset(->)(PQ) = overset(->)(SR)`
`text(Consider diagonal)\ \ overset(->)(AC):`
`overset(->)(AC) = overset(->)(AB) + overset(->)(BC) = overset(->)(AO) + overset(->)(OC)`
`overset(->)(QR) = overset(->)(QB) + overset(->)(BR) = 1/2(overset(->)(AB) + overset(->)(BC)) = 1/2overset(->)(AC)`
`overset(->)(PS) = overset(->)(PO) + overset(->)(OS) = 1/2(overset(->)(AO) + overset(->)(OC)) = 1/2overset(->)(AC)`
`:. overset(->)(QR) = overset(->)(PS)`
`text(S)text(ince)\ PQRS\ text(has equal opposite sides,)`
`PQRS\ text(is a parallelogram.)`
`PQRS` is a parallelogram, where `overset(->)(PQ) = underset~a` and `vec(PS) = underset~b`
Prove, using vectors, that the sum of the squares of the lengths of the diagonals is equal to the sum of the squares of the lengths of the sides. (3 marks)
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`text(See Worked Solution)`
`overset(->)(PR) = underset~a + underset~b,\ \ overset(->)(SQ) = underset~a – underset~b`
`overset(->)(PQ) = overset(->)(SR) = underset~a`
`overset(->)(PS) = overset(->)(QR) = underset~b`
`text(Prove)\ \ |underset~a + underset~b|^2 + |underset~a – underset~b|^2 = 2|underset~a|^2 + 2|underset~b|^2`
`|underset~a + underset~b|^2 + |underset~a – underset~b|^2` | `= (underset~a + underset~b) · (underset~a + underset~b) + (underset~a – underset~b)(underset~a – underset~b)` |
`= underset~a · underset~a + underset~b · underset~b + 2underset~a · underset~b + underset~a · underset~a + underset~b · underset~b – 2underset~a · underset~b` | |
`= |underset~a|^2 + |underset~b|^2 + |underset~a|^2 + |underset~b|^2` | |
`= 2|underset~a|^2 + 2|underset~b|^2\ \ …\ text(as required)` |
Let `OABCD` be a right square pyramid where `underset ~a = vec(OA),\ underset ~b = vec(OB),\ underset ~c = vec(OC)` and `underset ~d = vec(OD)`.
Show that `underset~a + underset~c = underset~b + underset~d`. (3 marks)
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`text(See Worked Solution)`
`text(Let)\ \ A=(p,–p,–k),`
`underset ~a` | `= overset(->)(OA) = punderset~i – punderset~j – qunderset~k` |
`underset ~b` | `= overset(->)(OB) = punderset~i + punderset~j – qunderset~k` |
`underset ~c` | `= overset(->)(OC) = −punderset~i + punderset~j – qunderset~k` |
`underset ~d` | `= overset(->)(OA) = −punderset~i – punderset~j – qunderset~k` |
`underset~a + underset~c` | `= −2qunderset~k` |
`underset ~b + underset ~d` | `= −2qunderset~k` |
`:. underset~a + underset~c = underset~b + underset~d`
A cube with side length 3 units is pictured below.
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i. `A(3, 0 , 0), \ \ G(0, 3, 3)`
`vec(AG)` | `= ((0), (3), (3)) – ((3), (0), (0)) = ((text{−3}), (3), (3))` | |
`|\ vec(AG)\ |` | `= sqrt (9 + 9 + 9)` | |
`= 3 sqrt 3\ text(units)` |
ii. | `H (3, 3, 3)` |
`vec(BH) = ((3), (3), (3))` |
`vec(AG) ⋅ vec(BH)` | `= |\ vec(AG)\ | ⋅ |\ vec(BH)\ |\ cos theta` |
`((text{−3}), (3), (3)) ⋅ ((3), (3), (3))` | `= sqrt (9 + 9 + 9) ⋅ sqrt (9 + 9 + 9) cos theta` |
`-9 + 9 + 9` | `= 27 cos theta` |
`cos theta` | `= 1/3` |
`theta` | `= 70.52…` |
`= 70^@32′` |
`ABCDEFGH` are the vertices of a rectangular prism.
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i. | `A(2, text{−2}, 0),` | `G(text{−2}, 2, 2)` |
`D(2, 2, 0),` | `F (text{−2}, text{−2}, 2)` |
`text(Midpoint)\ AG = ((1/2 (2 – 2)),(1/2 (text{−2} + 2)),(1/2 (0 + 2))) = ((0), (0), (1))`
`text(Midpoint)\ DF = ((1/2 (2 – 2)),(1/2 (2 – 2)),(1/2 (0 + 2))) = ((0), (0), (1))`
`text(S) text(ince midpoints are the same), AG and DF\ text(intersect.)`
ii. | `vec(AG) = ((text{−2}), (2), (2)) – ((2), (text{−2}), (0)) = ((text{−4}), (4), (2))` |
`vec(DF) = ((text{−2}), (text{−2}), (2)) – ((2), (2), (0)) = ((text{−4}), (text{−4}), (2))` |
`vec (AG) ⋅ vec (DF) = |\ vec (AG)\ | ⋅ |\ vec(DF)\ |\ cos theta`
`((text{−4}), (4), (2)) ⋅ ((text{−4}), (text{−4}), (2)) = sqrt 36 sqrt 36 cos theta`
`16 – 16 + 4` | `= 36 cos theta` |
`cos theta` | `= 1/9` |
`theta` | `= 83.62…` |
`= 83^@37′` |
Point `B` sits on the arc of a semi-circle with diameter `AC`.
Using vectors, show `angle ABC` is a right angle. (2 marks)
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`text(See Worked Solution)`
`text(Let)\ \ vec (OA) = underset~a, \ text(and)\ \ vec(OC)=underset~c`
`text(Prove) \ overset(->)(AB) ⊥ overset(->)(BC)`
`|underset~a| = |underset~b| = |underset~c|\ \ \ text{(radii)}`
`underset~c = – underset~a `
`overset(->)(AB) ⋅ overset(->)(BC)` | `= (underset~b-underset~a) (underset~c-underset~b)` |
`= underset~b · underset~c-|underset~b|^2-underset~a · underset~c + underset~a · underset~b` | |
`= underset~b · underset~c-|underset~b|^2 + underset~c · underset~c-underset~c · underset~b` | |
`= |underset~c|^2-|underset~b|^2` | |
`= 0` |
`:. \ ∠ABC \ text(is a right angle.)`
`OABD` is a trapezium in which `overset(->)(OA) = underset~a` and `overset(->)(OB) = underset~b`.
`OC` is parallel to `AB` and `DC : CB = 1:2`
Using vectors, express `overset(->)(DA)` in terms of `underset~a` and `underset~b`. (3 marks)
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`text(See Worked Solution)`
`overset(->)(DA) = overset(->)(DB) + overset(->)(BA)`
`overset(->)(BA) = underset~a – underset~b`
`text(S) text(ince) \ OC || AB \ \ text(and) \ \ OA || CB`
`=> OABC \ text(is a parallelogram)`
`overset(->)(OA)` | `= overset(->)(CB) = underset~a` |
`overset(->)(DC)` | `= (1)/(2) \ underset~a ` |
`overset(->)(DB)` | `= overset(->)(DC) + overset(->)(CB)` |
`= (3)/(2) \ underset~a` |
`:. \ overset(->)(DA)` | `= (3)/(2) \ underset~a + (underset~a – underset~b)` |
`= (5)/(2) \ underset~a – underset~b` |
Consider the two vector line equations
`underset~(v_1) = ((1),(4),(−2)) + lambda_1((3),(0),(−1)), qquad underset~(v_2) = ((3),(2),(2)) + lambda_2((4),(2),(−6))`
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i. `text(Solve simultaneously:)`
`1 + 3lambda_1` | `= 3 + 4lambda_2` | `\ \ …\ (1)` |
`4 + 0lambda_1` | `= 2 + 2lambda_2` | `\ \ …\ (2)` |
`−2 – lambda_1` | `= 2 – 6lambda_2` | `\ \ …\ (3)` |
`=> lambda_2 = 1\ \ \ text{(from (2))}`
`=>lambda_1 = 2\ \ \ text{(from (1) and (3))}`
`:.\ text(vector lines intersect)`
`text(P.O.I.) = ((1),(4),(−2)) + 2((3),(0), (−1)) = ((7),(4),(−4))`
ii. `underset~(v_1) = underset~(a_1) + lambda_1*underset~(b_1)`
`underset~(v_2) = underset~(a_2) + lambda_2*underset~(b_2)`
`costheta` | `= (underset~(b_1) · underset~(b_2))/(|underset~b_1||underset~b_2|)` |
`= (12 + 0 + 6)/(sqrt10 sqrt56)` | |
`= 0.7606…` |
`theta` | `= 40.479…` |
`= 40°29’\ \ (text(nearest minute))` |
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`a = −3, b = −3, c = 3, d = 2`
i. `text(Method 1)`
`overset(->)(OA) = underset~a = ((3),(1)),\ \ overset(->)(OB) = underset~b = ((−3),(−3))`
`overset(->)(AB)` | `= overset(->)(OB) – overset(->)(OA)` |
`= ((−3),(−3)) – ((3),(1))` | |
`= ((−6),(−4))` |
`underset~v` | `= underset~a + lambdaunderset~b` |
`= ((3),(1)) + lambda((−6),(−4))` | |
`= ((3),(1)) + 2((−3),(−2))` |
`:. a = 3, b = 1, c = −3, d = −2`
`text(Method 2)`
`overset(->)(BA)` | `= overset(->)(OA) – overset(->)(OB)` |
`= ((3),(1)) – ((−3),(−3))` | |
`= ((6),(4))` |
`underset~v = ((−3),(−3)) + 2((3),(2))`
`:. a = −3, b = −3, c = 3, d = 2`
ii. `underset~u = ((4),(6)) + lambda((−2),(3))`
`underset~v = ((3),(1)) + 2((−3),(−2))`
`((−2),(3)) · ((−3),(−2)) = 6 – 6 = 0`
`:. underset~u ⊥ underset~v`
iii. `((x),(y))= ((4),(6)) + lambda((−2),(3))`
`x = 4 – 2lambda\ \ \ …\ (1)`
`y = 6 + 3lambda\ \ \ …\ (2)`
`text(Substitute)\ \ lambda = (4 – x)/2\ \ text{from (1) into (2):}`
`y` | `= 6 + 3((4 – x)/2)` |
`y` | `= 6 + 6 – (3x)/2` |
`y` | `= −3/2x + 12` |
Which pair of line segments intersect at exactly one point
A. | `{(underset ~u = ((3), (2)) + lambda ((text{−1}),(2)) text{,} quad qquad 0 <= lambda <= 1), (underset ~v = ((2), (1)) + lambda ((2), (text{−4})) text{,} quad qquad 0 <= lambda <= 1):}` |
B. | `{(underset ~u = ((4), (1)) + lambda ((3), (text{−1})) text{,} quad qquad 0 <= lambda <= 1), (underset ~v = ((3), (2)) + lambda ((2), (2)) text{,} quad qquad 0 <= lambda <= 1):}` |
C. | `{(underset ~u = ((4), (0)) + lambda ((text{−3}),(6)) text{,} quad qquad 0 <= lambda <= 1), (underset ~v = ((0), (1)) + lambda ((1), (text{−2})) text{,} quad qquad 0 <= lambda <= 1):}` |
D. | `{(underset ~u = ((0), (2)) + lambda ((3), (text{−2})) text{,} quad qquad 0 <= lambda <= 1), (underset ~v = ((0), (1)) + lambda ((1), (1)) text{,} quad qquad 0 <= lambda <= 1):}` |
`D`
`text(S) text(ince)\ ((2), (text{−4})) = -2((text{−1}), (2)) and ((text{−3}), (6)) = -3((text{−1}), (2))`
`=> A and C\ text(are parallel lines.)`
`text(Consider)\ D:`
`3 lambda_1` | `= lambda_2` | `\ text{… (1)}` |
`2 – 2 lambda_1` | `= 1 + lambda_2` | `\ text{… (2)}` |
`text(Substitute)\ text{(1) into (2)}`
`2 – 2 lambda_1` | `= 1 + 3 lambda_1` |
`lambda_1` | `= 1/5` |
`lambda_2` | `= 3/5` |
`text(Similarly,)\ lambda_1, lambda_2\ text(in)\ B\ \ text(can be calculated)`
`text(and found to be outside)\ \ 0 <= lambda <= 1.`
`=> D`
`qquad underset ~a = ((3), (5), (1)) + lambda ((1), (3), (text{−2})),` and
`qquad underset ~b = ((text{−2}), (2), (text{−1})) + mu ((1), (text{−1}), (2))` (2 marks)
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i. `text(At point of intersection:)`
`3 + lambda` | `= -2 + mu\ \ text{… (1)}` |
`5 + 3 lambda` | `= 2 – mu\ \ text{… (2)}` |
`1 – 2 lambda` | `= -1 + 2 mu\ \ text{… (3)}` |
`(1) + (2)`
`8 + 4 lambda` | `= 0` |
`lambda` | `= -2,\ \ mu = 3` |
`text{Intersection (using}\ lambda = –2 text{)}:`
`((x), (y), (z)) = ((3 – 2 xx 1), (5 – 2 xx 3), (1 – 2 xx text{−2})) = ((1), (text{−1}), (5))`
ii. `text(If)\ \ (2, text{−2}, text{−10})\ \ text(lies on)\ underset ~b, ∃ mu\ \ text(that satisfies:)`
`-2 + mu` | `= 2\ \ text{… (1)}\ => \ mu = 4` |
`2 – mu` | `= text{−2}\ \ text{… (2)}\ => \ mu = 4` |
`-1 + 2 mu` | `= 5\ \ text{… (3)}\ => \ mu = 3` |
`=>\ text(No solution)`
`:. (2, text{−2}, 5)\ \ text(does not lie on)\ underset ~b.`
Use the vector form of the linear equations
`3x - 2y = 4` and `3y + 2x - 6 = 0`
to show they are perpendicular. (3 marks)
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`text(Proof)\ text{(See Worked Solutions)}`
`3x-2y` | `= 4` |
`3x` | `= 2y + 4` |
`3/2 x` | `=y+2` |
`x/(2/3)` | `= y + 2` |
`underset ~(v_1) = ((0), (-2)) + lambda ((2/3), (1))`
`3y + 2x-6` | `= 0` |
`2x` | `= -3y + 6` |
`-2/3 x` | `= y-2` |
`x/(-3/2)` | `= y-2` |
`underset ~(v_2) = ((0), (2)) + lambda ((-3/2), (1))`
`((2/3), (1)) ((-3/2), (1)) = -1 + 1 = 0`
`:. underset ~(v_1) _|_ underset ~(v_2)`