In ` A B C ,a , ca n dA` are given and `b_1,b_2` are two values of the third side `b` such that `b_2=2b_1dot` Then prove that `sinA=sqrt((9a^2-c^2)/(8c^2))`

Explanation

To solve the problem, we need to prove that

\[ \sin A = \sqrt{\frac{9a^2 - c^2}{8c^2}} \]

given that \( b_2 = 2b_1 \) and using the cosine rule in triangle \( ABC \).

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