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CGP EDU Academic Team
Published on: August 13, 2026
In a Δ Δ ABC, a, c, A are given and b 1 , b 2 are two values of the third side b such that b 2 = 2b 1 . Then sinA is equal to
A
B
C
D
None of these
Text Solution
Verified by ExpertsThe correct answer is:
B
We have cos A = 
⇒ ⇒ b 2 – 2bc cos A + (c 2 – a 2 ) = 0.
it is given that b 1 and b 2 are roots of this equation.
Therefore b 1 + b 2 = 2ccosA and b 1 b 2 = c 2 – a 2 ⇒ ⇒ 3b 1 = 2c cos A and 2b 1 2 = c 2 – a 2 (since b 2 = 2b 1 given)
⇒ ⇒ 2 
⇒ ⇒ 8c 2 (1 – sin 2 A) = 9c 2 – 9a 2 ⇒ ⇒ sin A = 
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