If A = 30°, then prove that :

sin 3A = 3 sin A - 4 sin³ A

If A = B = 45°, show that :

sin (A - B) = sin A cos B - cos A sin B

If 2sin A - 1 = 0 and A is an acute angle, the measure of angle A is :

1. 30°

2. 45°

3. 60°

4. 90°

If cos A (cos A - 1) = 0; the measure of angle A is :

1. 90° or 0°

2. 90° and 0°

3. 45° or 90°

4. 45° and 90°