Item2 The \(2\)-norm (a.k.a. the Euclidean norm): \(\|x\|_2 = \bigg(\sum_{i=1}^n |x_i|^2\bigg)^{1/2}.\) Note, if \(x \in \Cm \text{,}\) then \(x^\star x = \|x\|_2^2 \text{.}\)