证明cos(x+y)cos(x-y)= cos^2(x)-sin^2(y)

来源：学生作业帮编辑：百度作业网作业帮分类：数学作业时间：2024/07/04 19:01:08

令x+y=A,x-y=Bcos(x+y)cos(x-y)= cosAcosBx=(A+B)/2,y=(A-B)/2,代入cos^2(x)-sin^2(y)=cos2(A+B/2)-sin2(A-B/2)=[1+cos(A+B)-1+cos(A
-B）]/2=cosAcosB-sinAsinB+cosAcosB+sinAsinB）/2=cosAcosB所以cos(x+y)cos(x-y)= cos2x-sin2y

证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y sin(x+y)sin(x-y)=k,求cos^2x-cos^2y Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y) 请问怎么证明sinX+sin(X+Y)+sin(X+2Y)/cosX+cos(X+Y)+cos(X+2Y)=tan(X+ y =(cos^2) x - sin (3^x),求y' 化简y=sin^2(x)+2sin(x)cos(x)+3cos^2(x) 请问,如何证明sinx+siny=2*sin(x+y/2)*cos(x-y/2) 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 设sin(x+y)sin(x-y)=m,则cos^2x-cos^2y的值求导y=(1+sin^2 x)/(cos(x^2)) y=sin^2x+sinxcoswx+cos^2x 化简化简y=(cos x)^2+sin x -2 谢谢