# Second norm of matrix

1. Aug 26, 2004

### niko2000

Hi,
I have forgotten the formula for calculating the second norm of matrix. Does anyone know the formula?
Regards,
Niko

2. Aug 26, 2004

### Hurkyl

Staff Emeritus
Are you talking about the norm usually written as $||A||_2$? You simply consider the (mxn) matrix as an mn-tuple: the square of the norm is the sum of the squares of the entries.

3. Sep 17, 2004

### mathwonk

this is also called the pythagorean theorem. i'll bet you haven't really forgotten it. almost no one ever does: a^2 + b^2 = c^2.