In the diagram \(AB\) is a straight line.
Calculate the size of the angle marked \(x^{\circ}\), giving reasons for your answer. (3 marks)
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\(\text{Equilateral triangle}\ \ \Rightarrow\ \ \text{all angles}\ = 60^{\circ}\)
\(\text{Vertically opposite angles of 60° are equal (see diagram)}\)
\(x^{\circ} = 180-(90+60) = 30^{\circ}\ \ \text{(180° in straight line)}\)
Show Worked Solution
\(\text{Equilateral triangle}\ \ \Rightarrow\ \ \text{all angles}\ = 60^{\circ}\)
\(\text{Vertically opposite angles of 60° are equal (see diagram)}\)
\(x^{\circ} = 180-(90+60) = 30^{\circ}\ \ \text{(180° in straight line)}\)