Theorem 2on0

Description: Ordinal two is not zero. (Contributed by Scott Fenton, 17-Jun-2011)

	Ref	Expression
Assertion	2on0	|- 2o =/= (/)

Proof

Step	Hyp	Ref	Expression
1		df-2o	|- 2o = suc 1o
2		nsuceq0	|- suc 1o =/= (/)
3	1 2	eqnetri	|- 2o =/= (/)