Published by:
CGP EDU Academic Team
Published on: August 12, 2026
= 
if
A
θ = n π + 
, n ∈ Ι
, n ∈ Ι
B
θ = 2n π± 
, n ∈ Ι
, n ∈ Ι
C
θ = 2n π ± 
, n ∈ Ι
, n ∈ Ι
D
θ = n π + 
, n ∈ Ι
, n ∈ Ι
Text Solution
Verified by ExpertsThe correct answer is:
B
⇒ 2(4 cos 3 θ – 3 cos θ ) = 2 (2 cos 2 θ – 1) – 1 ⇒ 8 cos 3 θ – 4 cos 2 θ – 6 cos θ + 3 = 0
⇒ (4 cos 2 θ – 3) (2 cos θ – 1) = 0 ⇒ cos θ = 
, 
But when cos θ = 
then 2 cos 2 θ – 1 = 0
∴ rejecting this value, cos θ = 
is valid only ⇒ θ = 2n π ± 
, n ∈ Ι
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