More Sets

The following sets are defined using predicates:
 
Complex =
{ x + yi | x, y Î Reals } complex numbers, i = Ö - 1
[a , b ] = 
{x Î Reals | a £ x £ b } closed interval
(a , b ] = 
{x Î Reals | a < x £ b } half-open, half-closed interval
(a , b ) = 
{x Î Reals | a < x< b } open interval