| Step | Hyp | Ref | Expression | 
						
							| 1 |  | islpln2a.l |  |-  .<_ = ( le ` K ) | 
						
							| 2 |  | islpln2a.j |  |-  .\/ = ( join ` K ) | 
						
							| 3 |  | islpln2a.a |  |-  A = ( Atoms ` K ) | 
						
							| 4 |  | islpln2a.p |  |-  P = ( LPlanes ` K ) | 
						
							| 5 |  | oveq1 |  |-  ( Q = R -> ( Q .\/ R ) = ( R .\/ R ) ) | 
						
							| 6 | 2 3 | hlatjidm |  |-  ( ( K e. HL /\ R e. A ) -> ( R .\/ R ) = R ) | 
						
							| 7 | 6 | 3ad2antr2 |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( R .\/ R ) = R ) | 
						
							| 8 | 5 7 | sylan9eqr |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> ( Q .\/ R ) = R ) | 
						
							| 9 | 8 | oveq1d |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> ( ( Q .\/ R ) .\/ S ) = ( R .\/ S ) ) | 
						
							| 10 |  | simpll |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> K e. HL ) | 
						
							| 11 |  | simplr2 |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> R e. A ) | 
						
							| 12 |  | simplr3 |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> S e. A ) | 
						
							| 13 | 2 3 4 | 2atnelpln |  |-  ( ( K e. HL /\ R e. A /\ S e. A ) -> -. ( R .\/ S ) e. P ) | 
						
							| 14 | 10 11 12 13 | syl3anc |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> -. ( R .\/ S ) e. P ) | 
						
							| 15 | 9 14 | eqneltrd |  |-  ( ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) /\ Q = R ) -> -. ( ( Q .\/ R ) .\/ S ) e. P ) | 
						
							| 16 | 15 | ex |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( Q = R -> -. ( ( Q .\/ R ) .\/ S ) e. P ) ) | 
						
							| 17 | 16 | necon2ad |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( ( ( Q .\/ R ) .\/ S ) e. P -> Q =/= R ) ) | 
						
							| 18 |  | hllat |  |-  ( K e. HL -> K e. Lat ) | 
						
							| 19 | 18 | adantr |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> K e. Lat ) | 
						
							| 20 |  | simpr3 |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> S e. A ) | 
						
							| 21 |  | eqid |  |-  ( Base ` K ) = ( Base ` K ) | 
						
							| 22 | 21 3 | atbase |  |-  ( S e. A -> S e. ( Base ` K ) ) | 
						
							| 23 | 20 22 | syl |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> S e. ( Base ` K ) ) | 
						
							| 24 | 21 2 3 | hlatjcl |  |-  ( ( K e. HL /\ Q e. A /\ R e. A ) -> ( Q .\/ R ) e. ( Base ` K ) ) | 
						
							| 25 | 24 | 3adant3r3 |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( Q .\/ R ) e. ( Base ` K ) ) | 
						
							| 26 | 21 1 2 | latleeqj2 |  |-  ( ( K e. Lat /\ S e. ( Base ` K ) /\ ( Q .\/ R ) e. ( Base ` K ) ) -> ( S .<_ ( Q .\/ R ) <-> ( ( Q .\/ R ) .\/ S ) = ( Q .\/ R ) ) ) | 
						
							| 27 | 19 23 25 26 | syl3anc |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( S .<_ ( Q .\/ R ) <-> ( ( Q .\/ R ) .\/ S ) = ( Q .\/ R ) ) ) | 
						
							| 28 | 2 3 4 | 2atnelpln |  |-  ( ( K e. HL /\ Q e. A /\ R e. A ) -> -. ( Q .\/ R ) e. P ) | 
						
							| 29 | 28 | 3adant3r3 |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> -. ( Q .\/ R ) e. P ) | 
						
							| 30 |  | eleq1 |  |-  ( ( ( Q .\/ R ) .\/ S ) = ( Q .\/ R ) -> ( ( ( Q .\/ R ) .\/ S ) e. P <-> ( Q .\/ R ) e. P ) ) | 
						
							| 31 | 30 | notbid |  |-  ( ( ( Q .\/ R ) .\/ S ) = ( Q .\/ R ) -> ( -. ( ( Q .\/ R ) .\/ S ) e. P <-> -. ( Q .\/ R ) e. P ) ) | 
						
							| 32 | 29 31 | syl5ibrcom |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( ( ( Q .\/ R ) .\/ S ) = ( Q .\/ R ) -> -. ( ( Q .\/ R ) .\/ S ) e. P ) ) | 
						
							| 33 | 27 32 | sylbid |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( S .<_ ( Q .\/ R ) -> -. ( ( Q .\/ R ) .\/ S ) e. P ) ) | 
						
							| 34 | 33 | con2d |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( ( ( Q .\/ R ) .\/ S ) e. P -> -. S .<_ ( Q .\/ R ) ) ) | 
						
							| 35 | 17 34 | jcad |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( ( ( Q .\/ R ) .\/ S ) e. P -> ( Q =/= R /\ -. S .<_ ( Q .\/ R ) ) ) ) | 
						
							| 36 | 1 2 3 4 | lplni2 |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) /\ ( Q =/= R /\ -. S .<_ ( Q .\/ R ) ) ) -> ( ( Q .\/ R ) .\/ S ) e. P ) | 
						
							| 37 | 36 | 3expia |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( ( Q =/= R /\ -. S .<_ ( Q .\/ R ) ) -> ( ( Q .\/ R ) .\/ S ) e. P ) ) | 
						
							| 38 | 35 37 | impbid |  |-  ( ( K e. HL /\ ( Q e. A /\ R e. A /\ S e. A ) ) -> ( ( ( Q .\/ R ) .\/ S ) e. P <-> ( Q =/= R /\ -. S .<_ ( Q .\/ R ) ) ) ) |