用公式：y=u(x)×v(x),则y'=u'v+uv'y=f(u),f(u)=u(x),则y'=f'(u)×u'(x)y'=cosx/x+sinx×(-1/x^2)+1/sinx+x(-1/(sinx)^2)cosx再化简：得y'=(x*cosx-sinx)/x^2+(sinx-x*cosx)/sin^2x