满足cosx*cosy-sinx*siny=1/2的角xy有可能哪些

为什么sinx*cosy-cosx*siny=sin(x-y) 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 (sinx-siny)(sinx+siny)-(cosx+cosy)(cosx-cosy)等於? cosx-cosy=1/2,sinx-siny=1/3,sin(x+y)=RT sinx+cosy=1/3 cosx+siny=1/6 则 sin(x+y)? sinx+siny=-1/3 cosx+cosy=1/2,求sin(x+y)的值. sinx-siny=1/3,cosx-cosy=2/3,sin(x+y)=? sinx+cosy=1/3 cosx+siny=1/6 则sin(x+y)=?RT 满足cosx*cosy-sinx*siny=1/2的角xy有可能哪些 求所有满足方程组1.cosx/cosy=2cos^2y2.sinx/siny=2sin^2y的数对（x,y）,（x,y属于0到π/2) 已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).求过程! 已知sinx-siny=1/2,cosx-cosy=1/2,x、y均为锐角,求sin(x-y) 已知cos(x-y)cosx+sin(x-y)sinx=3/5,则cosy的值为 急!本人赶着数学作业!cosX+sinY=4/5 sinX+cosY=3/5 求sin(x+y) sinx+siny=1/2,cosx+cosy=（根号3）/3,求sin[(x-y)/2] sinx+siny=根号2/2 cosx+cosy=根号6/2 则sin（x+y）= sinx+siny=√2/2 cosx+cosy=√6/2 求sin(x+y)求解答. sinx+siny=√2/2 cosx+cosy=√6/2 求sin(x+y)求解答