Metamath Proof Explorer


Theorem spansncv

Description: Hilbert space has the covering property (using spans of singletons to represent atoms). Exercise 5 of Kalmbach p. 153. (Contributed by NM, 9-Jun-2004) (New usage is discouraged.)

Ref Expression
Assertion spansncv A C B C C A B B A span C B = A span C

Proof

Step Hyp Ref Expression
1 psseq1 A = if A C A A B if A C A B
2 oveq1 A = if A C A A span C = if A C A span C
3 2 sseq2d A = if A C A B A span C B if A C A span C
4 1 3 anbi12d A = if A C A A B B A span C if A C A B B if A C A span C
5 2 eqeq2d A = if A C A B = A span C B = if A C A span C
6 4 5 imbi12d A = if A C A A B B A span C B = A span C if A C A B B if A C A span C B = if A C A span C
7 psseq2 B = if B C B if A C A B if A C A if B C B
8 sseq1 B = if B C B B if A C A span C if B C B if A C A span C
9 7 8 anbi12d B = if B C B if A C A B B if A C A span C if A C A if B C B if B C B if A C A span C
10 eqeq1 B = if B C B B = if A C A span C if B C B = if A C A span C
11 9 10 imbi12d B = if B C B if A C A B B if A C A span C B = if A C A span C if A C A if B C B if B C B if A C A span C if B C B = if A C A span C
12 sneq C = if C C 0 C = if C C 0
13 12 fveq2d C = if C C 0 span C = span if C C 0
14 13 oveq2d C = if C C 0 if A C A span C = if A C A span if C C 0
15 14 sseq2d C = if C C 0 if B C B if A C A span C if B C B if A C A span if C C 0
16 15 anbi2d C = if C C 0 if A C A if B C B if B C B if A C A span C if A C A if B C B if B C B if A C A span if C C 0
17 14 eqeq2d C = if C C 0 if B C B = if A C A span C if B C B = if A C A span if C C 0
18 16 17 imbi12d C = if C C 0 if A C A if B C B if B C B if A C A span C if B C B = if A C A span C if A C A if B C B if B C B if A C A span if C C 0 if B C B = if A C A span if C C 0
19 ifchhv if A C A C
20 ifchhv if B C B C
21 ifhvhv0 if C C 0
22 19 20 21 spansncvi if A C A if B C B if B C B if A C A span if C C 0 if B C B = if A C A span if C C 0
23 6 11 18 22 dedth3h A C B C C A B B A span C B = A span C