[SOLVED] Projections on subspaces 1. The problem statement, all variables and given/known data I have some questions on this topic: 1) If I have an orthonormal basis for a subspace U and I have a vector A, and I want to find the orthogonal projection of A onto U, then I use the expression written here: http://mathworld.wolfram.com/VectorSpaceProjection.html 2) If I have found the orthogonal complement V to U, and I wish to find the projection of the vector A onto V, I can either: - use the expression in http://mathworld.wolfram.com/VectorSpaceProjection.html on the orthonormal set that spans V - or use A - proj(U)_A (the projection of A onto U) 3) I don't know if this is "legal", but I would like to draw your attention to my question in: https://www.physicsforums.com/showthread.php?t=207060 3. The attempt at a solution Can you guys confirm this? Sadly, in my book it is not written that well. Thanks in advance, sincerely Niles.