cos(x+y)*cos(x-y)=cos*cosx+sin*siny

来源：学生作业帮助网 编辑：作业帮 时间：2024/05/09 11:52:27

cos(x+y)*cos(x-y)=cos*cosx+sin*siny
cos(x+y)*cos(x-y)=cos*cosx+sin*siny

cos(x+y)*cos(x-y)=cos*cosx+sin*siny
cos(x+y)=cosx*cosy-sinx*siny
cos(x-y)=cosx*cosy+sinx*siny
则cos(x+y)*cos(x-y)
=(cos*cosx)*(cos*cosy) - (sin*sinx)*(sin*siny)
=(cos*cosx)*(1-sin*siny) - (1-cos*cosx)*(sin*siny)
=cos*cosx - (cos*cosx)*(sin*siny) - sin*siny + (cos*cosx)*(sin*siny）
=cos*cosx - sin*siny
这个……我证得应该是相减的关系
是不是题出错了,还是你打错了?
代入x=45°,y=45°就知道应该是相减的关系

cos(x)看到这个 cos(x)－cos(y)=? ：y' +y= cos x y= 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y 证明cos(x+y)cos(x-y)= cos^2(x)-sin^2(y) y=2cos x (sin x+cos x) 求解微分方程y+y=cos x y=(cos x-2)/(cos x-1)的值域 y=cos^2 x-cos x +1的值域y=cos^2 x+cos x +1的值域, y=(sin x + COS x)^2 cos(x+y)*cos(x-y)=cos*cosx+sin*siny 解微分方程y'=y/x+cos(y/x) 解微分方程y'=y/x+cos(y/x) y=cos(x+y) y对x的导数y=cos（x+y) y对x的导数 sin(x+y)sin(x-y)=k,求cos^2x-cos^2y 化简sin (x+y)sin x +cos (x+y)cos x= 若cos(x+y)cos(x-y)=1/3,则cos^x-sin^y=?^为平方 Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y) Cos x=1/7 Cos（x+y)=-11/14 x y 为锐角,求Cos y很急!