Theorem 9onn

Description: The ordinal 9 is a natural number. (Contributed by BTernaryTau, 4-Sep-2026)

	Ref	Expression
Assertion	9onn	Could not format assertion : No typesetting found for |- 9o e. _om with typecode |-

Proof

Step	Hyp	Ref	Expression
1		df-9o	Could not format 9o = suc 8o : No typesetting found for |- 9o = suc 8o with typecode |-
2		8onn	Could not format 8o e. _om : No typesetting found for |- 8o e. _om with typecode |-
3		peano2	Could not format ( 8o e. _om -> suc 8o e. _om ) : No typesetting found for |- ( 8o e. _om -> suc 8o e. _om ) with typecode |-
4	2 3	ax-mp	Could not format suc 8o e. _om : No typesetting found for |- suc 8o e. _om with typecode |-
5	1 4	eqeltri	Could not format 9o e. _om : No typesetting found for |- 9o e. _om with typecode |-