Thanks for the reply.
The first question is to just find the normal vector to the surface. I suppose that means the general formula for the normal in relation to x,y,z?
The next part is to find the normal at the point
Sorry, I'm very lost with this concept. I understand the normal to a plane is the cross-product of the 2 vectors by which it is bound, but I have no idea how to find the normal to a surface. I did find some material on the net but it's in such ambiguous mathematical terms I can't understand it cearly.
- Simon