I've been wrestling with this problem for several days. I really wanted to solve it myself, but at this point I just keep barking up the same wrong trees. Any help would be greatly appreciated. Here is the problem - I am trying to determine Vector N', given the following: Vector A = [5,3,1] Vector N = [3,2,-21] Vector A' = [5,3,2] <-- Vector A has moved by one unit in Z Furthermore, N is normal to A, N' is normal to A', and N' is to A' what N is to A So far I've determined the following: theta(A,A') = 9.172 deg = theta(N,N') AdotA' = 36 ScalarA = 5.916 ScalarN = 21.307 ScalarA' = 6.164 I really want to figure this out on my own, but I am convinced there is some simple relationship that I am missing. If someone could point me in the right direction I'd be grateful.