What symmetry statement can be made about the points $(a, b)$ and $(b, a)$?

The question is: if $a$ and $b$ are any two numbers, what symmetry statement can be made about the points $(a, b)$ and $(b, a)$?

I'm not sure whether this is a symmetry statements and whether it is the correct solution, but here's what I get

"the points $(a, b)$ and $(b, a)$ are symmetric with respect to the quarters if $a$ and $b$ have different signs"

• They are symmetric with respect to the main diagonal – Hagen von Eitzen Feb 10 '15 at 10:48
• Ah, you were first :P – mathreadler Feb 10 '15 at 10:53

They are equidistant to the line $x=y$, i.e. they "mirror" each other in this line.