Question

If 2 cosθ = √3, evaluate 3 sinθ – 4 sin³θ

(a) 3

(b) 4/3

(c) 1

(d) 2

Answer 1

Correct option is (c) 1

2cosθ = √3​

⇒ cosθ = \(\frac{\sqrt 3}2\)

⇒ θ = 30°

⇒ 3sinθ − 4sin³θ = sin3θ  [\(\because\) sin3θ = 3sin3θ − 4sin3θ]

= sin(3 × 30°)

= sin90°

= 1