What symbol should replace the question mark in the expression below
$$a\text{ ? }b$$
in order to express that $a$ and $b$ have opposite signs, i.e.:
$$a<0 \text{ when } b>0$$
$$a>0 \text{ when } b<0$$
The correct notation for “has opposite sign than”
notation
Best Answer
You could use $a b < 0$ for example. Or $a b \leq 0$ if $a$ or $b$ can be zero.