最好的方法是，既然我们已经有了梯度向量，就可以直接说,我们知道了切平面的法向量。
OK, the best way to it, now that we have the gradient vector, is actually to directly say oh, we know the normal vector to this plane.
求切平面方程的一般方法是先求切平面的法向量(借助偏导)，再用点法式写出切平面的方程。
The common method to quadric surface equation is to get the Normal Component first, and then write out the equation through dot method.
当然也有另一种方法，就是用参数方程表示这两条直线，用两条直线的方向向量作外积，从而得到切平面的法向量。
Another way to do it, of course, would provide actually parametric equations of these lines, get vectors along them and then take the cross-product to get the normal vector to the plane.
这就是切平面的，或者说这个曲面的法向量。
OK, and that's going to be the normal vector to the surface or to the tangent plane.
这就是切平面的，或者说这个曲面的法向量。
OK, and that's going to be the normal vector to the surface or to the tangent plane.
应用推荐