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Prove that a^(2) sin 2B + b^(2) sin 2A =...

Prove that `a^(2) sin 2B + b^(2) sin 2A = 4 Delta`

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`a^(2) sin 2B + b^(2) sin 2A`
`= 4R^(2) [sin^(2) A (2 sin B cos B) + sin^(2) B (2 sin A cos A)]` [using sine rule]
`= 8R^(2) sin A sin B (sin A cos B + sin B cos A)`
`=8R^(2) sin A sin B sin (A + B)`
`= 8R^(2) sin A sin B C = 4Delta`
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