Hi!

I just need to be sure I have used the summation sign correctly. That is:

Correct me if I'm wrong, but this - when applied to a n x n matrix A - would be the square root of the sum of all individual elements squared, except the elements on the diagonal (where i = j); essentially the "length" of all elements (again without the diagonal).

It's probably very easy, but I just want to make sure I'm not mistaken!

Thank you in advance!