Does anyone know of a non-awkward way to notate the interval between two numbers when you don't know which number is larger?
For example when describing the remainder term in Taylor's theorem, one claims the existence of a number $\xi$ that's between $a$ (the center of the expansion) and $x$ (where you're evaluating the expansion). It seems wrong to write $[a,x]$ or $[x,a]$ since these numbers could come in either order (or in fact be equal). Some possibilities:
- $[a,b]\cup[b,a]$
- $[\min\{a,b\},\max\{a,b\}]$
- $[\frac{a+b-|a-b|}{2},\frac{a+b+|a-b|}{2}]$
Honestly I think these are all terrible. Does anyone know of anything better?