I don't understand how if U and W are subspaces of V such that and then U + W will be S-invariant even if U and W aren't. Can someone explain this to me? I need to understand this to make an operator S for 2x2 matrices.
I don't understand how if U and W are subspaces of V such that and then U + W will be S-invariant even if U and W aren't. Can someone explain this to me? I need to understand this to make an operator S for 2x2 matrices.