Theorem 6p3e9

Description: 6 + 3 = 9. (Contributed by NM, 11-May-2004)

	Ref	Expression
Assertion	6p3e9	$$⊢6+3=9$$

Proof

Step	Hyp	Ref	Expression
1		df-3	$$⊢3=2+1$$
2	1	oveq2i	$$⊢6+3=6+2+1$$
3		6cn	$$⊢6\in ℂ$$
4		2cn	$$⊢2\in ℂ$$
5		ax-1cn	$$⊢1\in ℂ$$
6	3 4 5	addassi	$$⊢6+2+1=6+2+1$$
7	2 6	eqtr4i	$$⊢6+3=6+2+1$$
8		df-9	$$⊢9=8+1$$
9		6p2e8	$$⊢6+2=8$$
10	9	oveq1i	$$⊢6+2+1=8+1$$
11	8 10	eqtr4i	$$⊢9=6+2+1$$
12	7 11	eqtr4i	$$⊢6+3=9$$