sinx+cosy=1/3 cosx+siny=1/6 则sin(x+y)=?
问题描述：
sinx+cosy=1/3 cosx+siny=1/6 则sin(x+y)=?
RT
答
sinx+cosy=1/3 ,cosx+siny=1/6(sinx+cosy)^2 = 1/9,(cosx+siny)^2 = 1/36sin^2x +cos^2y +2sinxcosy +cos^2x+sin^2y +2cosxsiny = 1/9+1/36 = 5/36sin^2x +cos^2x+sin^2y +cos^2y +2sinxcosy +2cosxsiny = 5/361 + 1...