Question

If A = 30°; 3 sin A − 4 sin³ A is equal to ______.

Options

• cos 3А

• tan 3А

• sin 3А

• cot 3А

Answer 1

If A = 30°; 3 sin A − 4 sin³ A is equal to sin 3А.

Explanation:

Substituting A = 30° into the expression:

\[3\sin 30^\circ - 4\sin^3 30^\circ = 3\left(\frac{1}{2}\right) - 4\left(\frac{1}{2}\right)^3 = \frac{3}{2} - 4\left(\frac{1}{8}\right) = \frac{3}{2} - \frac{1}{2} = 1\]