有cos(x+y)=cosxcosy-sinxsiny又将题目所给式子左右平方,在两个式子左右对应相加为: cos^2x+cos^2y+2cosxcsoy+sin^2x+sin^2y-2sinxsiny=13/36 由cos^2x+sin^2x=1 cos^2y+sin^2y=1 可得 1+2cosxcsoy+1-2sinxsiny=13/36 2cosxcsoy-2sinxsin=59/36 cosxcosy-sinxsiny=59/72
已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
1个回答
相关问题
-
已知cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=
-
已知1+cosx-siny+sinx*siny=0,1-cosx-cosy+sinx*cosy=0.求Sinx.
-
已知sinX-sinY=-1\/2,cosX-cosY=1\/3求sin(X+Y)=?
-
已知2cosx+cosy=2/3,2sinx-siny=3/4,求cos(x+y).
-
已知sinx+siny=0.4,cosx+cosy=1.2,则cos(x-y)=______.
-
已知sinx+cosy=1/3,siny+cosx=1/2,则sin(x-y)=
-
已知sinx-siny=-1/2,cosx+cosy=√7/2,求tan(x-y)=
-
若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=?
-
1、if sinx-siny= -1/3,cosx-cosy=1/2,then cos(x-y)=?
-
sinx-siny=-√3/3 cosx-cosy=-1/3 则cos(x-y)