cos(x+y)-cosx如何等于-2sin[(2x+y)/2]sin(y/2),
函数y=cos^3x+sin^2x-cosx的最大值等于?
化简sin(2x-y)*sin y+cos(2x-y)*sin y
sinx*sin(x+y)+cosx*cos(x+y)等于?
化简sin(x+y)sinx+cos(x+y)cosx等于?
请问怎么证明sinX+sin(X+Y)+sin(X+2Y)/cosX+cos(X+Y)+cos(X+2Y)=tan(X+
sin(x+y)sin(x-y)=k,求cos^2x-cos^2y
y =(cos^2) x - sin (3^x),求y'
证明COS(X+Y)COS(X-Y)=COS^2X-SIN^2Y
y=sin^2x+2sinx*cosx+3cos^2x
函数y=sin²x-cos²x+2cosx-2的最大值是?
y=sin²X+2sinX*cosX+3COS²X的最大值是?
Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y)