Question

please answer my question ​

Answer 1

Step-by-step explanation:

Given: θ = 30°.

(i)

cos 3θ = 4 cos³θ - 3 cosθ

⇒ cos 3(30°) = 4 cos³(30) - 3 cos(30°)

⇒ cos 90° = 4 (3√3/8) - 3(√3/2)

⇒ cos 90° = (3√3/2) - (3√3/2)

⇒ 0 = 0.

(ii)

Given: sin 3θ = 3 sinθ - 4 sin³θ

⇒ sin 3(30°) = 3 sin(30°) - 4 sin³(30°)

⇒ sin 90° = 3(1/2) - 4(1/8)

⇒ 1 = (3/2) - (1/2)

⇒ 1 = 2/2

⇒ 1 = 1

Hope it helps!

Answer 2

cos 3θ = 4 cos³θ - 3 cosθ

cos 3(30°) = 4 cos³(30) - 3 cos(30°)

cos 90° = 4 (3√3/8) - 3(√3/2)

cos 90° = (3√3/2) - (3√3/2)

0 = 0.