Question

If θ = 30° then 3 sin θ − 4 sin³ θ = ______.

Options

• 0

• −1

• 1

• `−1/2`

Answer 1

If θ = 30° then 3 sin θ − 4 sin³ θ = 1.

Explanation:

sin 30° = `1/2`

3 sin 30° = 3 × `1/2` = `3/2`

4 sin³ 30° = 4 × `(1/2)^3 = 4 xx 1/8 = 1/2`

3 sin 30° − 4 sin³ 30°

= `3/2 − 1/2`

= 1