Question

化简sin^2Xsin^2Y+cos^2Xcos^2Y-0.5cos2Xcos2Y

Answer 1

(sinx)^2(siny)^2+(cosx)^2(cosy)^2-1/2*cos2xcos2y

=(1-cos2x)/2*(1-cos2y)/2+(1+cos2x)/2*(1+cos2y)/2-1/2*cos2xcos2y

=(1-cos2x-cos2y+cos2xcos2y)/4+(1+cos2x+cos2y+cos2xcos2y)/4-1/2*cos2xcos2y

=(1+cos2xcos2y)/2-1/2*cos2xcos2y

=1/2