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Trigonometry, 2ADV EQ-Bank 14

Prove that  \(\sec ^2 x+\sec x\, \tan x=\dfrac{1}{1-\sin x}\).   (3 marks)

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\(\text{Proof (See Worked Solution)}\)

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\(\text {LHS }\) \(=\sec ^2 x+\sec x \, \tan x\)
  \(=\dfrac{1}{\cos ^2 x}+\dfrac{1}{\cos x} \cdot \dfrac{\sin x}{\cos x}\)
  \(=\dfrac{1+\sin x}{\cos ^2 x}\)
  \(=\dfrac{1+\sin x}{1-\sin ^2 x}\)
  \(=\dfrac{1+\sin x}{(1-\sin x)(1+\sin x)}\)
  \(=\dfrac{1}{1-\sin x}\)

Filed Under: Trig Identities and Harder Equations Tagged With: Band 4, smc-6412-20-Prove Identity

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