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°

If 2sin 3A - 1 = 0 ; the value of angle A is :

1. 20°

2. 60°

3. 10°

4. 30°

If 3tan² A - 1 = 0 and angle A is acute, the measure of angle A is :

1. 20°

2. 45°

3. 60°

4. 30°