Theorem 5onn

Description: The ordinal 5 is a natural number. (Contributed by BTernaryTau, 4-Sep-2026)

	Ref	Expression
Assertion	5onn	Could not format assertion : No typesetting found for |- 5o e. _om with typecode |-

Proof

Step	Hyp	Ref	Expression
1		df-5o	Could not format 5o = suc 4o : No typesetting found for |- 5o = suc 4o with typecode |-
2		4onn	$$⊢4_{𝑜}\in \mathrm{\omega }$$
3		peano2	$$⊢4_{𝑜}\in \mathrm{\omega }\to \mathrm{suc}{4}_{𝑜}\in \mathrm{\omega }$$
4	2 3	ax-mp	$$⊢\mathrm{suc}{4}_{𝑜}\in \mathrm{\omega }$$
5	1 4	eqeltri	Could not format 5o e. _om : No typesetting found for |- 5o e. _om with typecode |-