The ImaginaryUnit function returns a square root of $\mathrm{-1}$ modulo n, if possible. If not possible, an error message is displayed.

If there is more than one imaginary unit, only one of them is returned.

$\mathrm{with}\left(\mathrm{NumberTheory}\right)\:$

$\mathrm{ImaginaryUnit}\left(5\right)$

$3$

$3^2\mathbf{mod}5$

$4$

$\mathrm{ImaginaryUnit}\left(6\right)$

Error, (in NumberTheory:-ImaginaryUnit) -1 does not have a square root modulo 6

$\mathrm{seq}\left(i^2\mathbf{mod}6\,i=0..5\right)$

$0,1,4,3,4,1$

The NumberTheory[ImaginaryUnit] command was introduced in Maple 2016.

For more information on Maple 2016 changes, see Updates in Maple 2016.