Sometimes you may want to check if a number is treated as complex number in GeoGebra, as function such as
y() do not work with real numbers. As there is no such command as
IsComplex you currently have to employ a small trick to check if the number
a is complex:
complex = IsDefined[sqrt(a) + sqrt(-a)] ∧ (a ≠ 0).
a = 2 + 0i, also pass this test. If you just want to check if the imaginary part of a complex number
ais not 0 you can use
y(a) != 0.