Question #b0676

1 Answer
P dilip_k
Apr 23, 2016

LHS
=sin(x+y)sin(x-y)
=(sinxcosy+cosxsiny)*(sinxcosy-cosxsiny)
=(sin^2xcos^2y-cos^2xsin^2y)
=(sin^2x(1-sin^2y)-(1-sin^2x)sin^2y)
=(sin^2x-cancel(sin^2x*sin^2y)-sin^2y+cancel(sin^2xsin^2y))
=(sin^2x-sin^2y)=RHS

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