I've seen that referred to as the antidiagonal. Not sure how common the usage of that is though.
Thank you.
Searching for "antidiagonal" gave other terms also used:
subsidiary diagonal
secondary diagonal.
Subsidiary diagonal can be confushed with superdiagonal/subdiagonal when refering to tridiagonal matrices.
The "main diagonal" is the "primary diagonal" and the "antidiagonal is the "secondary diagonal".
I like that.
Again, Thank you.
Example: 2x2 matrix
The diagonal from the upper left to the lower right is identified as "main diagonal".
The trace(A) is the sum of the elements along the main diagonal.
Or do you have a reference/resource that might have a name for this diagonal?
]]>