Answers

2014-06-13T03:42:39+05:30
(cosx-cosy)^2 + (Sinx-siny)^2
 = cos^2x + cos^2y -2cosxcosy + sin^2x + sin^2y - 2sinxsiny
 = (  cos^2x +  sin^2x) + (cos^2y +  sin^2y ) - 2(cosxcosy + sinxsiny)
 = 1+1 - 2cos(x-y)
 = 2(1 - cos(x-y))
 = 2*( 2sin^2(x-y)/2
 = 4sin^2(x-y)/2
Hence proved 

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