Definition:Set of Residue Classes/Least Absolute
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Definition
Let $\eqclass a m$ be the residue class of $a$ (modulo $m$).
Except when $r = \dfrac m 2$, we can choose $r$ to be the integer in $\eqclass a m$ which has the smallest absolute value.
In that exceptional case we have:
- $-\dfrac m 2 + m = \dfrac m 2$
and so:
- $-\dfrac m 2 \equiv \dfrac m 2 \pmod m$
Thus $r$ is defined as the least absolute residue of $a$ (modulo $m$) if and only if:
- $-\dfrac m 2 < r \le \dfrac m 2$