1.sin(π/4+x)*sin(π/4+x)-cos(π/4+x)*cos(π/4+x)
问题描述：
1.sin(π/4+x)*sin(π/4+x)-cos(π/4+x)*cos(π/4+x)
2.cosα*cos(α+β)-sin(α+β)*sinα
3.cos(α-β)*cos(β-ν)-sin(α-β)*cos(β-ν)
答
1. sin(π/4+x)*sin(π/4+x)-cos(π/4+x)*cos(π/4+x) =-{[cos(π/4+x)]^2-[sin(π/4+x)]^2}=-cos[2*(π/4+x)]=-cos(π/2+2x)=sin(2x)2.cosα*cos(α+β)-sin(α+β)*sinα =cos[α+(α+β)]=cos(2α+β)3.cos(α-β...