Question

If tan 2A = cot (A – 18°), where 2A is an acute angle, find the value of A

Answer 1

tan 2A = cot (A – 18°)

cot (90° – 2A) = cot (A – 18°)

(∵ cot (90° – θ) = tan θ)

90° – 2A = A – 18°

3A = 108°

A = 36°