1. The problem statement, all variables and given/known data Let u1,u2,u3 be an orthonormal basis for R3 and consider M as the plane with equation x1+2x2-2x3=0. Find the matrix of orthogonal reflection in that plane with respect to the given basis. 2. Relevant equations 3. The attempt at a solution In previous exercises , I had a matrix A given and was asked to find the equation of the plane that the matrix was projected or reflected on. To do that I solved the equation (A-I)x=0 . (The nullspace/kernel minus the identity matrix) .. I was thinking that maybe to solve this current exercise, I could maybe use the method from the previous exercises but use it backwards ... and find the matrix A? But im not sure if im thinking right, or how to attack the problem... Would appreciate help...thanks.