Published by:
CGP EDU Academic Team
Published on: August 13, 2026
If in a Δ ABC, the sides b, a, c are in A.P. then-
A
acos2 
+ c cos2 
= 
+ c cos2 =
B
c cos2 
+ b cos2 
= 
+ b cos2 =
C
bcos2 
+ a cos2 
= 
+ a cos2 =
D
2 sin 
= cos 
= cos
Text Solution
Verified by ExpertsThe correct answer is:
B
b + c = 2a
Option B :
⇒ c cos2 B/2 + b cos2 C/2 = 3a/2
⇒ 2c cos2 B/2 + 2b cos2 C/2 = 3a
⇒ c (1 + cos B) + b(1 + cos C) = 3a
⇒ b + c + c cos B + b cos C = 3a
⇒ b + c + a = 3a
⇒ b + c = 2a which is in A.P.
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