Metamath Proof Explorer


Theorem his5

Description: Associative law for inner product. Lemma 3.1(S5) of Beran p. 95. (Contributed by NM, 29-Jul-1999) (New usage is discouraged.)

Ref Expression
Assertion his5 A B C B ih A C = A B ih C

Proof

Step Hyp Ref Expression
1 hvmulcl A C A C
2 ax-his1 B A C B ih A C = A C ih B
3 1 2 sylan2 B A C B ih A C = A C ih B
4 3 3impb B A C B ih A C = A C ih B
5 4 3com12 A B C B ih A C = A C ih B
6 ax-his3 A C B A C ih B = A C ih B
7 6 3com23 A B C A C ih B = A C ih B
8 7 fveq2d A B C A C ih B = A C ih B
9 hicl C B C ih B
10 cjmul A C ih B A C ih B = A C ih B
11 9 10 sylan2 A C B A C ih B = A C ih B
12 11 3impb A C B A C ih B = A C ih B
13 12 3com23 A B C A C ih B = A C ih B
14 ax-his1 B C B ih C = C ih B
15 14 3adant1 A B C B ih C = C ih B
16 15 oveq2d A B C A B ih C = A C ih B
17 13 16 eqtr4d A B C A C ih B = A B ih C
18 5 8 17 3eqtrd A B C B ih A C = A B ih C