Theorem 4p5e9

Description: 4 + 5 = 9. (Contributed by SN, 24-Aug-2026)

	Ref	Expression
Assertion	4p5e9	$$⊢4+5=9$$

Proof

Step	Hyp	Ref	Expression
1		df-5	$$⊢5=4+1$$
2	1	oveq2i	$$⊢4+5=4+4+1$$
3		4cn	$$⊢4\in ℂ$$
4		ax-1cn	$$⊢1\in ℂ$$
5	3 3 4	addassi	$$⊢4+4+1=4+4+1$$
6		4p4e8	$$⊢4+4=8$$
7	6	oveq1i	$$⊢4+4+1=8+1$$
8		8p1e9	$$⊢8+1=9$$
9	7 8	eqtri	$$⊢4+4+1=9$$
10	2 5 9	3eqtr2i	$$⊢4+5=9$$