1. The problem statement, all variables and given/known data Prove that (AxB) is perpendicular to A *We know that it is in the definition but this requires an actual proof. This is what I did on the exam because it was quicker than writing out the vectors and crossing and dotting them. 2. Relevant equations X dot Y = 0 when they are perpendicular AxB= epsilonijk(AjBk)i 3. The attempt at a solution AxB= epsilonijk(AjBk)i so (AxB) dot A = AxB= epsilonijk(AjBk)iAi = AxB= epsilonijkAiAjBk which means that i=j because we have both Ai and Aj. If i=j then epsilon=0, so the value of the dot product is 0, which means the angle between them is 90.