Question

If cos A (cos A − 1) = 0; the measure of angle A is ______.

Options

• 90° or 0°

• 90° and 0°

• 45° or 90°

• 45° and 90°

Answer 1

If cos A (cos A − 1) = 0; the measure of angle A is 90° or 0°.

Explanation:

Setting each factor to zero gives either cos A = 0 or cos A − 1 = 0 ⇒ cos A = 1. For an angle A within standard ranges (0° ≤ A ≤ 90°), cos 90° = 0 and 0° = 1, so the measure of angle A is 90° or 0°.