- #1
Astrum
- 269
- 5
I'm really confused about the double sum given by my textbook. Here's what it says:
If A is an nxm matrix, its length is the square root of the sum of its squares of all its entries.
[tex]\left|A\right|^{2}=\sum^{n}_{i=1}\sum^{m}_{j=1}a_{i,j}^{2}[/tex]
The double sum is what has me caught up. How do you visualize this, and how do you compute it?
If A is an nxm matrix, its length is the square root of the sum of its squares of all its entries.
[tex]\left|A\right|^{2}=\sum^{n}_{i=1}\sum^{m}_{j=1}a_{i,j}^{2}[/tex]
The double sum is what has me caught up. How do you visualize this, and how do you compute it?