d
___ f[(sin ^2)x]
dx
=(f[(sin ^2)x])'=f'((sinx)^2)*2sinx*cosx=g[(sin ^2)x]sin(2x)(f[(sin ^2)x])'=f'((sinx)^2)*2sinx*cosx为什么？这是链式求导，若h(x)=f(g(x)) 　　则h'(x)=f'(g(x))g'(x)