Find value of x, if :

cos(2x - 6°) = cos² 30° - cos² 60°

In each case given below, find the value of angle A, where 0° ≤ A ≤ 90°.

(i) sin (90° - 3A). cosec 42° = 1

(ii) cos (90° - A). sec 77° = 1

Evaluate :

sin² 34° + sin² 56° + 2 tan 18° tan 72° - cot² 30°