求证cosx-cosy=-2sin (x+y/2)*sin (x-y/2)
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求证cosx-cosy=-2sin(x+y/2)*sin(x-y/2)求证cosx-cosy=-2sin(x+y/2)*sin(x-y/2)求证cosx-cosy=-2sin(x+y/2)*sin(x
求证cosx-cosy=-2sin (x+y/2)*sin (x-y/2)
求证cosx-cosy=-2sin (x+y/2)*sin (x-y/2)
求证cosx-cosy=-2sin (x+y/2)*sin (x-y/2)
x=(x+y)/2+(x-y)/2
y=(x+y)/2-(x-y)/2
所以左边=cos[(x+y)/2+(x-y)/2]-cos[(x+y)/2-(x-y)/2]
={cos[(x+y)/2]cos[(x-y)/2]-sin[(x+y)/2]sin[(x-y)/2]}-{cos[(x+y)/2]cos[(x-y)/2]+sin[(x+y)/2]sin[(x-y)/2]}
=-2sin[(x+y)/2]sin[(x-y)/2]
=右边
命题得证
求证cosx-cosy=-2sin (x+y/2)*sin (x-y/2)
已知2cosx=3cosy求证:3cosx-2cosy/2siny-3sinx=tan(x+y)
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证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2
cosx*cosy=1,sin(x+y)=?
为什么sinx*cosy-cosx*siny=sin(x-y)
cosx-cosy=1/2,sinx-siny=1/3,sin(x+y)=RT
sinx-siny=1/3,cosx-cosy=2/3,sin(x+y)=?
sinx+siny=-1/3 cosx+cosy=1/2,求sin(x+y)的值.
(COSx)^2--(COSy)^2=(根号3)/2,求SIN(X+Y).SIN(X-Y)=
sin(x+y)sin(x-y)=m,则(cosx)^2-(cosy)^2的值为求具体过程,谢谢!
sin(x+y)*sin(y-x)=m,cosx的平方-cosy的平方?
已知sinx-siny=1/2,cosx-cosy=1/2,x、y均为锐角,求sin(x-y)
求证:sin(x-y)/(sinx-siny)=cos[(x-y)/2]/cos[(x+y)/2](cosy-cosx)/(sinx-siny)=tan[(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
sinx+siny=1/2,cosx+cosy=(根号3)/3,求sin[(x-y)/2]