Published by:
CGP EDU Academic Team
Published on: August 14, 2026
Find the number of all values of θ ∈ [0, 10.5] satisfying the equation cos 6 θ + cos 4 θ + cos 2 θ + 1 = 0.
Text Solution
Verified by ExpertsThe correct answer is:
17
(17)
cos6 θ + cos 4 θ + cos2 θ + 1 = 0 ⇒ 2cos4 θ cos2 θ + (1+ cos4 θ ) = 0
⇒ 2cos4 θ cos2 θ + 2cos22 θ = 0 ⇒ 2cos2 θ (cos4 θ + cos2 θ ) = 0
⇒ cos2 θ (2cos3 θ cos θ ) = 0 ⇒ 
, 
, 
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