# squares or inner

1. ### [SOLVED] Best approximation/least squares/inner product

Let f^*=\sum_{j=0}^n c_j^* \phi_j be the best approximation with respect to f for the least squares, where {\phi_0,\phi_1,...,\phi_n} is a linear independent set. Show that \parallel f-f^* \parallel={\parallel f \parallel}^2-{\parallel f^* \parallel}^2 where the norm is the one induced by the...