Originally Posted by

**zhandele** It seems to me there's a lot of gray area. For instance, a familiar theorem says that the diagonals of a parallelogram bisector each other. An elementary proof is easy to find, and I assume all of us do this some time in high school. But suppose you want to prove it using vectors. That we might not learn until we take linear algebra. And linear algebra does belong in this forum. I think. Maybe we could use another forum about linear algebra.

I'm working through Norman Wildberger's WildLinAlg videos now (so far as I know, this video series is not used in any credit classes anywhere, but it's a very interesting treatment of the subject). He includes a lecture on 3D geometry. I'm thinking of asking a question about one of his exercises. Since it's part of a linear algebra program, I figure I should post it in this forum. Would I be right to do so?