Metamath Proof Explorer


Theorem 4p4e8ALT

Description: A shorter proof of 4p4e8 if 6p2e8 was moved up. The most clean way to do this would be to start with 7p2e9 , then go 6p2e8 , 6p3e9 , etc., which is still inelegant. The idea here is that using 4 = 2 + 2 and 2cn is shorter than using 4 = 3 + 1 , 3cn , and ax-1cn . This also works with 5p4e9 . (Contributed by SN, 24-Aug-2026) (Proof modification is discouraged.) (New usage is discouraged.)

Ref Expression
Assertion 4p4e8ALT 4 + 4 = 8

Proof

Step Hyp Ref Expression
1 4cn 4
2 2cn 2
3 1 2 2 addassi 4 + 2 + 2 = 4 + 2 + 2
4 4p2e6 4 + 2 = 6
5 4 oveq1i 4 + 2 + 2 = 6 + 2
6 6p2e8 6 + 2 = 8
7 5 6 eqtri 4 + 2 + 2 = 8
8 2p2e4 2 + 2 = 4
9 8 oveq2i 4 + 2 + 2 = 4 + 4
10 3 7 9 3eqtr3ri 4 + 4 = 8