Published by:
CGP EDU Academic Team
Published on: August 13, 2026
If A + B + C = 
, then cos 2A + cos2B + cos2C is equal to
Text Solution
Verified by ExpertsThe correct answer is:
D
A + B + C = 
⇒ cos 2A + cos 2B + cos 2C = 2 cos (A + B).cos (A – B) + 1 – 2 sin 2 C
= 
.cos(A – B) – 2 sin 2 C + 1 ( A + B + C = 
)
= –2 sin C {cos(A – B) + sin C} + 1 = –2 sin C {cos(A – B) + sin ( 
– (A + B))} + 1
= –2 sin C {cos(A – B) – cos (A + B)} + 1 = 1 – 4 sin A sin B sin C.
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