Theorem 4p3e7

Description: 4 + 3 = 7. (Contributed by NM, 11-May-2004)

	Ref	Expression
Assertion	4p3e7	$$⊢4+3=7$$

Proof

Step	Hyp	Ref	Expression
1		df-3	$$⊢3=2+1$$
2	1	oveq2i	$$⊢4+3=4+2+1$$
3		4cn	$$⊢4\in ℂ$$
4		2cn	$$⊢2\in ℂ$$
5		ax-1cn	$$⊢1\in ℂ$$
6	3 4 5	addassi	$$⊢4+2+1=4+2+1$$
7	2 6	eqtr4i	$$⊢4+3=4+2+1$$
8		df-7	$$⊢7=6+1$$
9		4p2e6	$$⊢4+2=6$$
10	9	oveq1i	$$⊢4+2+1=6+1$$
11	8 10	eqtr4i	$$⊢7=4+2+1$$
12	7 11	eqtr4i	$$⊢4+3=7$$