sinX+sinY=1 cosX+cosY=0 求cos(2X)+cos(2Y)的值

cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=? 已知cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)= 已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y) cosx-cosy=4/1,sinx-siny=3/1求cos(x-y) 若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=? sinx-siny=-√3/3 cosx-cosy=-1/3 则cos(x-y) 证明sinx+cos(x+y)siny/cosx-sin(x+y)siny=tan(x+y) 若3sinx*2+2siny*2=1 且3(sinx+cosx)*2+2(siny+cosy)*2=1求cos(2x+2y) sinX+sinY=1 cosX+cosY=0 求cos(2X)+cos(2Y)的值 已知1+cosx-siny+sinx*siny=0,1-cosx-cosy+sinx*cosy=0.求Sinx. 已知1+cosx-siny+sinx*siny=0,1-cosx-cosy+sinx*cosy=0,求sinx的值 sinx+siny=3/5,cosx+cosy=4/5,求cos(x-y)sinx^2+cosx^2才＝1啊 不要给我sinx^2+siny^2=1啊 拜托大家帮帮忙老大 过程啊啊啊 若sinx-siny=-1/3,cosx-cosy=1/2,则cos（x-y）=? 已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).求过程! 设cosx+cosy=1/2,sinx+siny=1/4,求cos(x-y)的值 设cosX+cosY=1/2,sinX+sinY =1/4,求cos（X-Y）的值 已知sinx-siny=-1/3,cosx-cosy=1/2,求COS（X—Y）＝ 已知sinx+siny=1/2,cosx+cosy=1/3,求cos²((x-y)/2)