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.

one of the first links on google

… 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!