Target Mathematics

2.18: Tan–cot identity and linear combination

0606/22/O/N/16 — Question 6 · 8 marks

(i)
Prove that cosx1+tanxsinx1+cotx=cosxsinx\dfrac{\cos x}{1 + \tan x} - \dfrac{\sin x}{1 + \cot x} = \cos x - \sin x.
[4]
(ii)
Hence solve the equation cosx1+tanxsinx1+cotx=3sinx4cosx\dfrac{\cos x}{1 + \tan x} - \dfrac{\sin x}{1 + \cot x} = 3\sin x - 4\cos x for 180°<x<180°-180^{\degree} < x < 180^{\degree}.
[4]