- #1
hbweb500
- 41
- 1
I am working on a problem that uses the notation:
[tex]
\sum_{i,j=1}^n A_{i,j}
[/tex]
Where A is an (n x n) matrix. I am a little unsure of what the summation is over, due to the odd notation "i,j = 1". My first guess is that this is shorthand for
[tex]
\sum_{i=1}^n \sum_{j=1}^n A_{i,j}
[/tex]
But I am wondering if it could also mean the sum over the diagonal elements of the matrix, i.e.:
[tex]
\sum_{i=1}^n A_{i,i}
[/tex]
I am guessing it is the first, but I want to make absolutely sure.
[tex]
\sum_{i,j=1}^n A_{i,j}
[/tex]
Where A is an (n x n) matrix. I am a little unsure of what the summation is over, due to the odd notation "i,j = 1". My first guess is that this is shorthand for
[tex]
\sum_{i=1}^n \sum_{j=1}^n A_{i,j}
[/tex]
But I am wondering if it could also mean the sum over the diagonal elements of the matrix, i.e.:
[tex]
\sum_{i=1}^n A_{i,i}
[/tex]
I am guessing it is the first, but I want to make absolutely sure.