Published by:
CGP EDU Academic Team
Published on: August 14, 2026
If in a triangle ABC sines of angles A and B satisfy the
equation 4 x 2 – 2 
x + 1 = 0, then cos (A – B) is equal to -
A
0
B
1/2
C
1/ 
D
/2
Text Solution
Verified by ExpertsThe correct answer is:
B
sin A + sin B = 
sin A . sin B = ¼ , Let A > B [ A ≠ B]
⇒ sin 2 A + sin 2 B + 2 × ¼ = 6/4
⇒ sin 2 A + sin 2 B = 1 ⇒ sin 2 A = cos 2 B,
⇒ cos B = sin A ⇒ B = 90 0 – A
⇒ A + B = C = 90 0 Also sin A sin B = cos B sin B = ¼ ,
⇒ sin2 B = ½ ⇒ 2B = 30
0 or 150 0 ⇒ B = 15
0 or 75 0 ⇒ B = 15
0 , A = 75 0 , ⇒ A – B = 60 0 ⇒ cos (A – B) = ½ .
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