If A + B + C = π, prove that

sin2 A – sin2 B + sin2 C = 2sin A cos B sin C


= sin2 A – sin2 B + sin2 C


Using formula ,






Using ,





since A + B + C = π



And sin(π – A) = sinA




Using , cos2A = 1 – 2sin2A











= 2sinAcosBsinC


= R.H.S


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