和差化积的所有公式

和差化积公式共八个

sinx+siny=2sin(x/2+y/2)cos(x/2-y/2)

sinx-siny=2cos(x/2+y/2)sin(x/2-y/2)

cosx+cosy=2cos(x/2+y/2)cos(x/2-y/2)

cosx-cosy=-2sin(x/2+y/2)sin(x/2-y/2)

tgx±tgy=sin(x±y)/cosxcosy

ctgx±ctgy=±sin(x±y)/sinxsiny

sinx±cosx=sqrt2*sin(x±45°)=±sqrt2*cos(x-+45°) (x-+45°)---括号中的-+号是±的相反写法，即"-"号在上"+"号在下。

1-cos2x=2sin^2x

1+cos2x=2cos^2x