Published by:
CGP EDU Academic Team
Published on: August 13, 2026
If in a triangle ABC, a 4 + b 4 + c 4 = 2a 2 b 2 + b 2 c 2 + 2a 2 c 2 , then sin A is equal to -
A
B
C
D
None of these
Text Solution
Verified by ExpertsThe correct answer is:
B
We know cos A = 
⇒ b 4 + c 4 + a 4 + 2b 2 c 2 –2a 2 b 2 –2a 2 c 2 =4b 2 c 2 cos 2 A
⇒ a 4 + b 4 + c 4 = 2a 2 c 2 + 2a 2 b 2 + b 2 c 2
(–2 + 4 cos 2 A)
comparing with given equation:–2 + 4 cos 2 A = 1
⇒ cos 2 A = 
⇒ sin 2 A = 
or sin A = 
.
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