1. The problem statement, all variables and given/known data Prove: In R3if a and b are orthogonal vectors, then for every nonzero vector u, we have proja(projbu)=0 2. Relevant equations I know the dot product of a and b is zero 3. The attempt at a solution Based on the definition of projection I eventually got to (ab) in the numerator which is zero and was done. So how can I write this out with words only?