Metamath Proof Explorer


Theorem normlem8

Description: Lemma used to derive properties of norm. (Contributed by NM, 30-Jun-2005) (New usage is discouraged.)

Ref Expression
Hypotheses normlem8.1 A
normlem8.2 B
normlem8.3 C
normlem8.4 D
Assertion normlem8 A+BihC+D=AihC+BihD+AihD+BihC

Proof

Step Hyp Ref Expression
1 normlem8.1 A
2 normlem8.2 B
3 normlem8.3 C
4 normlem8.4 D
5 his7 ACDAihC+D=AihC+AihD
6 1 3 4 5 mp3an AihC+D=AihC+AihD
7 his7 BCDBihC+D=BihC+BihD
8 2 3 4 7 mp3an BihC+D=BihC+BihD
9 6 8 oveq12i AihC+D+BihC+D=AihC+AihD+BihC+BihD
10 3 4 hvaddcli C+D
11 ax-his2 ABC+DA+BihC+D=AihC+D+BihC+D
12 1 2 10 11 mp3an A+BihC+D=AihC+D+BihC+D
13 1 3 hicli AihC
14 2 4 hicli BihD
15 1 4 hicli AihD
16 2 3 hicli BihC
17 13 14 15 16 add42i AihC+BihD+AihD+BihC=AihC+AihD+BihC+BihD
18 9 12 17 3eqtr4i A+BihC+D=AihC+BihD+AihD+BihC