证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2
证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2
sinx+siny=-1/3 cosx+cosy=1/2,求sin(x+y)的值.
证明sin(x+y)=sinx*cosy+cosx*siny的过程
已知sinx-siny=1/2,cosx-cosy=1/2,x、y均为锐角,求sin(x-y)
sinx+siny=√2/2 cosx+cosy=√6/2 求sin(x+y)求解答.
sinx+siny=1/2,cosx+cosy=(根号3)/3,求sin[(x-y)/2]
sinx+siny=2/5,cosx+cosy=6/5,求cos(2x-2y)
若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=?
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)
已知sinx减siny等于负三分之二(sinx-siny=-2/3);cosx加cosy等于三分之二(cosx+cosy
已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).