已知sinx+siny=-0.5,cosx-cosy=0.5,且X.Y都是锐角,则tan(x-y)=急
问题描述：
已知sinx+siny=-0.5,cosx-cosy=0.5,且X.Y都是锐角,则tan(x-y)=
急
答
tan(x-y)=(tanx-tany)/(1+tanx*tany)=[(sinxcosy-cosxsinx)/(cosxcosy) / [(cosxcosy+sinxsiny)/(cosxcosy)]=(sinxcosy-cosxsinx)/(cosxcosy+sinxsiny)=sin(x-y)/cos(x-y)(sinx+siny)²=0.25sin²x+sin²...