Question

三角函数证明题,谁能帮忙看看求证(cosx-siny)/(cosy-sinx)=(cosy+sinx)/(cosx+si

Answer 1

因sin^2x+cos^2x=sin^2y+cos^2y=1

则cos^2x-sin^2y=cos^2y-sin^2x

即(cosx-siny)(cosx+siny)=(cosy-sinx)(cosy+sinx)

得(cosx-siny)/(cosy-sinx)=(cosy+sinx)/(cosx+siny)