Theorem 9on

Description: Ordinal 9 is an ordinal number. (Contributed by BTernaryTau, 4-Sep-2026)

	Ref	Expression
Assertion	9on	Could not format assertion : No typesetting found for |- 9o e. On 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		8on	Could not format 8o e. On : No typesetting found for |- 8o e. On with typecode |-
3	2	onsuci	Could not format suc 8o e. On : No typesetting found for |- suc 8o e. On with typecode |-
4	1 3	eqeltri	Could not format 9o e. On : No typesetting found for |- 9o e. On with typecode |-