已知x,y∈(0,2∏),且满足方程:cosx+cosy-cos(x+y)=3/2,求x,y
已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
已知x,y是实数且满足sinx*cosy=1,则cos(x+y)=
已知x-y=3/π且cosx-cosy=1/3,则cos(x+y)等于多少
已知:x-y=120度,且cosx+cosy=1/3,则cos(x+y)=
高一数学 已知x-y=120度,且cosx+cosy=1/3,则cos(x+y)=?
COSX+COSY-COS(X+Y)=3/2求角X Y分别是多少?谢谢好心的师姐师兄啦.
已知sinx+siny=1/2,cosx+cosy=1/3,求cos²((x-y)/2)
已知sinx-siny=-1/3,cosx-cosy=1/2,求COS(X—Y)=
已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).
已知2cos(2x+y)=cosy,求tan(x+y)tany的值
sinx+siny=2/5,cosx+cosy=6/5,求cos(2x-2y)
已知函数f(x)满足f(0)=1,且对x,y∈R,恒有f(x+y)+f(x-y)=2f(x)*cosy.求f(x)