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Metamath Proof Explorer

Theorem 1p3e4

Description: 1 + 3 = 4. (Contributed by SN, 19-Nov-2025)

		Ref	Expression
	Assertion	1p3e4	$⊢ 1 + 3 = 4$

Step	Hyp	Ref	Expression
1		df-3	$⊢ 3 = 2 + 1$
2	1	oveq2i	$⊢ 1 + 3 = 1 + 2 + 1$
3		ax-1cn	$⊢ 1 \in ℂ$
4		2cn	$⊢ 2 \in ℂ$
5	3 4 3	addassi	$⊢ 1 + 2 + 1 = 1 + 2 + 1$
6		1p2e3	$⊢ 1 + 2 = 3$
7	6	oveq1i	$⊢ 1 + 2 + 1 = 3 + 1$
8		3p1e4	$⊢ 3 + 1 = 4$
9	7 8	eqtri	$⊢ 1 + 2 + 1 = 4$
10	2 5 9	3eqtr2i	$⊢ 1 + 3 = 4$