Metamath Proof Explorer


Theorem normlem7tALT

Description: Lemma used to derive properties of norm. Part of Theorem 3.3(ii) of Beran p. 97. (Contributed by NM, 11-Oct-1999) (New usage is discouraged.) (Proof modification is discouraged.)

Ref Expression
Hypotheses normlem7t.1 A
normlem7t.2 B
Assertion normlem7tALT S S = 1 S A ih B + S B ih A 2 B ih B A ih A

Proof

Step Hyp Ref Expression
1 normlem7t.1 A
2 normlem7t.2 B
3 fveq2 S = if S S = 1 S 1 S = if S S = 1 S 1
4 3 oveq1d S = if S S = 1 S 1 S A ih B = if S S = 1 S 1 A ih B
5 oveq1 S = if S S = 1 S 1 S B ih A = if S S = 1 S 1 B ih A
6 4 5 oveq12d S = if S S = 1 S 1 S A ih B + S B ih A = if S S = 1 S 1 A ih B + if S S = 1 S 1 B ih A
7 6 breq1d S = if S S = 1 S 1 S A ih B + S B ih A 2 B ih B A ih A if S S = 1 S 1 A ih B + if S S = 1 S 1 B ih A 2 B ih B A ih A
8 eleq1 S = if S S = 1 S 1 S if S S = 1 S 1
9 fveq2 S = if S S = 1 S 1 S = if S S = 1 S 1
10 9 eqeq1d S = if S S = 1 S 1 S = 1 if S S = 1 S 1 = 1
11 8 10 anbi12d S = if S S = 1 S 1 S S = 1 if S S = 1 S 1 if S S = 1 S 1 = 1
12 eleq1 1 = if S S = 1 S 1 1 if S S = 1 S 1
13 fveq2 1 = if S S = 1 S 1 1 = if S S = 1 S 1
14 13 eqeq1d 1 = if S S = 1 S 1 1 = 1 if S S = 1 S 1 = 1
15 12 14 anbi12d 1 = if S S = 1 S 1 1 1 = 1 if S S = 1 S 1 if S S = 1 S 1 = 1
16 ax-1cn 1
17 abs1 1 = 1
18 16 17 pm3.2i 1 1 = 1
19 11 15 18 elimhyp if S S = 1 S 1 if S S = 1 S 1 = 1
20 19 simpli if S S = 1 S 1
21 19 simpri if S S = 1 S 1 = 1
22 20 1 2 21 normlem7 if S S = 1 S 1 A ih B + if S S = 1 S 1 B ih A 2 B ih B A ih A
23 7 22 dedth S S = 1 S A ih B + S B ih A 2 B ih B A ih A