cos^2(α+β)+cos^2(α-β)-cos2αcos2β

问题描述:

cos^2(α+β)+cos^2(α-β)-cos2αcos2β

cos²(α+β)=0.5[cos(2α+2β)+1]=0.5os2αcos2β-0.5sin2αsin2β+0.5
cos²(α-β)=0.5[cos(2α-2β)+1]=0.5cos2αcos2β+0.5sin2αsin2β+0.5
从而原式=1