Here's what I got to prove where '.' is dot. A.B=A.C Then B=C True or false? If true, prove it in general terms, if false, provide a counter-example. Ok, I just need some body to comment on my little proof here, and any guidelines to make it more thorough or whatnot. I know that the dot product is commutative, A.(B+C)=A.B +A.C, but not sure if it really needs to be in my proof or not. Proof ------ Say A.B=N and A.C=N (where N is a scalar number) so if N=N Then A.B=A.C If I cancel the A's, I get B=C. Is that a good way to approach that, or is there a better way of expressing it?