复合函数的求导法则:
如果u=g(x)在点x可导 ,而y=f(u)在点u=g(x)可导,则复合函数y=f[g(x)]在点x可导,且其导数为dy/dx=f'(u)g'(x)或dy/dx=(dy/du)(du/dx).
由此:
令u=sinx^2,
dy/dx=f'(u)*2sinx*cosx,
dy=f'(u)*2sinx*cosx*dx