Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

You are told that $\cos a = \frac{3}{5}$, with $0^\circ < a < 90^\circ$. Show your working, and without using a calculator to evaluate $a$,

(i)[3]

Find the exact value of $\sin(a - 30^\circ)$.

(ii)[4]

find the exact value of $\tan 2a$, and therefore the exact value of $\tan 3a$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “State or imply $\sin a=\frac{4}{5}$.” …