A square has two diagonals, so how can I to name the separate diagonals if I want to distinguish one from another?
I mean something like the up to down diagonal and the down to up diagonal. Do you have any better suggestions?
A square has two diagonals, so how can I to name the separate diagonals if I want to distinguish one from another?
I mean something like the up to down diagonal and the down to up diagonal. Do you have any better suggestions?
You could borrow a term from heraldry and call them the diagonal dexter and the diagonal sinister. The dexter diagonal would be the one from upper left to lower right, and the sinister diagonal the other one. (In heraldry these things are bends).
As John Lawler said in the comments, you could use compass points:
NW-SE and NE-SW
If you don't wish to use compass points, another option would be:
bottom-left to top-right and bottom-right to top-left
Of course, in a mathematical context you can label the four corners of the square clockwise as A, B, C, D, and then talk about "the line AC" and "the line BD".