【解】复合函数求导步骤：①先简化函数，令u=x^2，则y=sinu。y对u求导得dy/du=cosu②再u对x求导得du/dx=2x总的导数就等于上述各步的导数的乘积，就是dy/dx=dy/du*du/dx=cosu*2x=cosx^2*2x
