若sinx-siny=-1/3,cosx-cosy=1/2,则cos(x-y)=?
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/07/03 10:56:07
若sinx-siny=-1/3,cosx-cosy=1/2,则cos(x-y)=?
cosx-cosy=1/2 ,sinx-siny=-1/3
分别两边平方
(cosx)^2-2cosxcosy+(cosy)^2=1/4
(sinx)^2-2sinxsiny+(siny)^2=1/9
相加
且(cosx)^2+(sinx)^2=1 (cosy)^2+(siny)^2=1
2-2(cosxcosy+sinxsiny)=1/4+1/9=13/36
cos(x-y)=cosxcosy+sinxsiny
=(2-13/36)/2
=59/72
分别两边平方
(cosx)^2-2cosxcosy+(cosy)^2=1/4
(sinx)^2-2sinxsiny+(siny)^2=1/9
相加
且(cosx)^2+(sinx)^2=1 (cosy)^2+(siny)^2=1
2-2(cosxcosy+sinxsiny)=1/4+1/9=13/36
cos(x-y)=cosxcosy+sinxsiny
=(2-13/36)/2
=59/72
若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=?
cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=?
若sinx-siny=-1/3,cosx-cosy=1/2,则cos(x-y)=?
已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
已知sinx-siny=-1/3,cosx-cosy=1/2,求COS(X—Y)=
cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
1、if sinx-siny= -1/3,cosx-cosy=1/2,then cos(x-y)=?
已知sinx+siny=1/2,cosx+cosy=1/3,求cos²((x-y)/2)
设cosX+cosY=1/2,sinX+sinY =1/4,求cos(X-Y)的值
已知sinx+siny=(√2)/4,cosx+cosy=1/2,求cos(x-y)的值.
sinX+sinY=1 cosX+cosY=0 求cos(2X)+cos(2Y)的值
已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).