| Step |
Hyp |
Ref |
Expression |
| 1 |
|
hlatjcom.j |
|- .\/ = ( join ` K ) |
| 2 |
|
hlatjcom.a |
|- A = ( Atoms ` K ) |
| 3 |
1 2
|
hlatj32 |
|- ( ( K e. HL /\ ( P e. A /\ Q e. A /\ R e. A ) ) -> ( ( P .\/ Q ) .\/ R ) = ( ( P .\/ R ) .\/ Q ) ) |
| 4 |
1 2
|
hlatjcom |
|- ( ( K e. HL /\ P e. A /\ R e. A ) -> ( P .\/ R ) = ( R .\/ P ) ) |
| 5 |
4
|
3adant3r2 |
|- ( ( K e. HL /\ ( P e. A /\ Q e. A /\ R e. A ) ) -> ( P .\/ R ) = ( R .\/ P ) ) |
| 6 |
5
|
oveq1d |
|- ( ( K e. HL /\ ( P e. A /\ Q e. A /\ R e. A ) ) -> ( ( P .\/ R ) .\/ Q ) = ( ( R .\/ P ) .\/ Q ) ) |
| 7 |
3 6
|
eqtrd |
|- ( ( K e. HL /\ ( P e. A /\ Q e. A /\ R e. A ) ) -> ( ( P .\/ Q ) .\/ R ) = ( ( R .\/ P ) .\/ Q ) ) |