已知sinx=3/5,x∈(π/2,π),求【sin(x+y)+sin(x-y)】/【cos(x+y)+cos(x-y)
cos(x+y)sinx-sin(x+y)cosx
证明COS(X+Y)COS(X-Y)=COS^2X-SIN^2Y
y =(cos^2) x - sin (3^x),求y'
sin(x+y)sin(x-y)=k,求cos^2x-cos^2y
求证:sin(x-y)/(sinx-siny)=cos[(x-y)/2]/cos[(x+y)/2]
Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y)
1.y=cos^4x+sin^4x 求周期 2.y=(sin2x+sin(2x+π/3))/( cos2x+cos(2x
sin(x+y)-sinx=2cos(x+1/2y)sin(1/2y)的详细证明步骤.
cos(x+y)=?sin(x+y)=?
已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).
sinx*sin(x+y)+cosx*cos(x+y)等于?
化简sin(x+y)sinx+cos(x+y)cosx等于?