sinx=1-sinycosx=-cosy(1-siny)^2+(-cosy)^2=11-2siny+siny^2+cosy^2=11-2siny+1=1siny=1/2siny=sinx-1cosy=-cosx(sinx-1)^2+(-cosx)^2=1sinx^2-2sinx+1+cosx^2=11-2sinx+1=1sinx=1/2cosx^2+cosy^2=1-sinx^2+1-siny^2=2-sinx^2-siny^2=2-1/4-1/4=3/2
若sinx+siny=1,cosx+cosy=0,求cos2x+cos2y的值
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