Theorem 1p4e5

Description: 1 + 4 = 5. (Contributed by SN, 24-Aug-2026)

	Ref	Expression
Assertion	1p4e5	|- ( 1 + 4 ) = 5

Proof

Step	Hyp	Ref	Expression
1		df-4	|- 4 = ( 3 + 1 )
2	1	oveq2i	|- ( 1 + 4 ) = ( 1 + ( 3 + 1 ) )
3		ax-1cn	|- 1 e. CC
4		3cn	|- 3 e. CC
5	3 4 3	addassi	|- ( ( 1 + 3 ) + 1 ) = ( 1 + ( 3 + 1 ) )
6		1p3e4	|- ( 1 + 3 ) = 4
7	6	oveq1i	|- ( ( 1 + 3 ) + 1 ) = ( 4 + 1 )
8		4p1e5	|- ( 4 + 1 ) = 5
9	7 8	eqtri	|- ( ( 1 + 3 ) + 1 ) = 5
10	2 5 9	3eqtr2i	|- ( 1 + 4 ) = 5