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 ABCBihAC=ABihC

Proof

Step Hyp Ref Expression
1 hvmulcl ACAC
2 ax-his1 BACBihAC=ACihB
3 1 2 sylan2 BACBihAC=ACihB
4 3 3impb BACBihAC=ACihB
5 4 3com12 ABCBihAC=ACihB
6 ax-his3 ACBACihB=ACihB
7 6 3com23 ABCACihB=ACihB
8 7 fveq2d ABCACihB=ACihB
9 hicl CBCihB
10 cjmul ACihBACihB=ACihB
11 9 10 sylan2 ACBACihB=ACihB
12 11 3impb ACBACihB=ACihB
13 12 3com23 ABCACihB=ACihB
14 ax-his1 BCBihC=CihB
15 14 3adant1 ABCBihC=CihB
16 15 oveq2d ABCABihC=ACihB
17 13 16 eqtr4d ABCACihB=ABihC
18 5 8 17 3eqtrd ABCBihAC=ABihC