Description: The complex numbers form a set. This axiom is redundant in the presence
of the other axioms (see cnexALT ), but the proof requires the axiom of
replacement, while the derivation from the construction here does not.
Thus, we can avoid ax-rep in later theorems by invoking Axiom ax-cnex instead of cnexALT . Use cnex instead. (Contributed by Mario
Carneiro, 17-Nov-2014)(New usage is discouraged.)