Question

If sin 3A = cos (A – 26°), where 3A is an acute angle, find the value of A.

Answer 1

cos 𝜃 = sin (90° - 𝜃)

⇒ cos (A – 26) = sin (90° − (A − 26°))

⇒ sin 3A = sin (90° − (A – 26))

Equating angles on both sides

3A = 90° − A + 26°

`4A = 116° A = 116/4 = 29^@`

`∴ A = 29^@`