Published by:
CGP EDU Academic Team
Published on: August 11, 2026
cos4x cos8x − cos5x cos9x = 0 if
Text Solution
Verified by ExpertsThe correct answer is:
CHECK THE SOLUTION.
(a,b,c)
cos4x cos8x − cos5x cos9x = 0 ⇒ 2cos4x cos8x = 2cos5x cos 9x
⇒ cos12x + cos4x = cos14x + cos4x ⇒ 14x = 2n π ± (12x)
⇒ 2x = 2n π or 26x = 2n π⇒ x = n π or 
∴ sinx = 0 or sin13x = 0
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