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The expression $\frac{(a+b+c)(b+c-a)(c+a-b)(a+b-c)}{4b^2c^2}$ is : |
$\cos 2A$ $1 + \cos A$ $1 - \cos A$ $\sin^2 A$ |
$\sin^2 A$ |
Let, $E=\frac{2s.2(s-a)2.(s-b)2.(s-c)}{4b^2c^2}=\frac{4}{b^2c^2}Δ^2=\frac{4}{b^2c^2}(\frac{1}{2}bc\sin A)^2=\sin^2 A$ |
