Calculating normals.

Umm...Could someone explain to me...In raw equations if it all possible. (with an example; i forgot all the fancy terms i learned in math classes)

I'd REALLY appreciate this.

[chowe6685]

one of the first links on google
http://www.flipcode.com/cgi-bin/knowledge.cgi?showunit=59

[john]

... but you don't *calculate* normals; you *define* normals!

The normals for the verticies of a triangle for a sphere are different than the normals of the triangle with the same verticies if that same triangle was on a plane, for example!