L2-Norm

A vector $\vec a$ has the $L_2$ -Norm:

\left \| \vec a \right \|_{2} = \sqrt{\sum_{k=1}^n|a_k|^2}

$n$ : Dimensions $a_k$ : $k$ -th element of $a$

The $L_2$ -Distance between two vectors $\vec a$ and $\vec b$ is:

d \left ( \vec a, \vec b \right ) = \sqrt{\sum_{k=1}^n|a_k - b_k|^2}