| Step | Hyp | Ref | Expression | 
						
							| 1 |  | 2wlkd.p |  |-  P = <" A B C "> | 
						
							| 2 |  | 2wlkd.f |  |-  F = <" J K "> | 
						
							| 3 |  | 2wlkd.s |  |-  ( ph -> ( A e. V /\ B e. V /\ C e. V ) ) | 
						
							| 4 |  | 2wlkd.n |  |-  ( ph -> ( A =/= B /\ B =/= C ) ) | 
						
							| 5 |  | 2wlkd.e |  |-  ( ph -> ( { A , B } C_ ( I ` J ) /\ { B , C } C_ ( I ` K ) ) ) | 
						
							| 6 | 1 2 3 4 5 | 2wlkdlem9 |  |-  ( ph -> ( { A , B } C_ ( I ` ( F ` 0 ) ) /\ { B , C } C_ ( I ` ( F ` 1 ) ) ) ) | 
						
							| 7 | 1 2 3 | 2wlkdlem3 |  |-  ( ph -> ( ( P ` 0 ) = A /\ ( P ` 1 ) = B /\ ( P ` 2 ) = C ) ) | 
						
							| 8 |  | preq12 |  |-  ( ( ( P ` 0 ) = A /\ ( P ` 1 ) = B ) -> { ( P ` 0 ) , ( P ` 1 ) } = { A , B } ) | 
						
							| 9 | 8 | 3adant3 |  |-  ( ( ( P ` 0 ) = A /\ ( P ` 1 ) = B /\ ( P ` 2 ) = C ) -> { ( P ` 0 ) , ( P ` 1 ) } = { A , B } ) | 
						
							| 10 | 9 | sseq1d |  |-  ( ( ( P ` 0 ) = A /\ ( P ` 1 ) = B /\ ( P ` 2 ) = C ) -> ( { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) <-> { A , B } C_ ( I ` ( F ` 0 ) ) ) ) | 
						
							| 11 |  | preq12 |  |-  ( ( ( P ` 1 ) = B /\ ( P ` 2 ) = C ) -> { ( P ` 1 ) , ( P ` 2 ) } = { B , C } ) | 
						
							| 12 | 11 | 3adant1 |  |-  ( ( ( P ` 0 ) = A /\ ( P ` 1 ) = B /\ ( P ` 2 ) = C ) -> { ( P ` 1 ) , ( P ` 2 ) } = { B , C } ) | 
						
							| 13 | 12 | sseq1d |  |-  ( ( ( P ` 0 ) = A /\ ( P ` 1 ) = B /\ ( P ` 2 ) = C ) -> ( { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) <-> { B , C } C_ ( I ` ( F ` 1 ) ) ) ) | 
						
							| 14 | 10 13 | anbi12d |  |-  ( ( ( P ` 0 ) = A /\ ( P ` 1 ) = B /\ ( P ` 2 ) = C ) -> ( ( { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) /\ { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) ) <-> ( { A , B } C_ ( I ` ( F ` 0 ) ) /\ { B , C } C_ ( I ` ( F ` 1 ) ) ) ) ) | 
						
							| 15 | 7 14 | syl |  |-  ( ph -> ( ( { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) /\ { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) ) <-> ( { A , B } C_ ( I ` ( F ` 0 ) ) /\ { B , C } C_ ( I ` ( F ` 1 ) ) ) ) ) | 
						
							| 16 | 6 15 | mpbird |  |-  ( ph -> ( { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) /\ { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) ) ) | 
						
							| 17 | 1 2 | 2wlkdlem2 |  |-  ( 0 ..^ ( # ` F ) ) = { 0 , 1 } | 
						
							| 18 | 17 | raleqi |  |-  ( A. k e. ( 0 ..^ ( # ` F ) ) { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) <-> A. k e. { 0 , 1 } { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) ) | 
						
							| 19 |  | c0ex |  |-  0 e. _V | 
						
							| 20 |  | 1ex |  |-  1 e. _V | 
						
							| 21 |  | fveq2 |  |-  ( k = 0 -> ( P ` k ) = ( P ` 0 ) ) | 
						
							| 22 |  | fv0p1e1 |  |-  ( k = 0 -> ( P ` ( k + 1 ) ) = ( P ` 1 ) ) | 
						
							| 23 | 21 22 | preq12d |  |-  ( k = 0 -> { ( P ` k ) , ( P ` ( k + 1 ) ) } = { ( P ` 0 ) , ( P ` 1 ) } ) | 
						
							| 24 |  | 2fveq3 |  |-  ( k = 0 -> ( I ` ( F ` k ) ) = ( I ` ( F ` 0 ) ) ) | 
						
							| 25 | 23 24 | sseq12d |  |-  ( k = 0 -> ( { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) <-> { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) ) ) | 
						
							| 26 |  | fveq2 |  |-  ( k = 1 -> ( P ` k ) = ( P ` 1 ) ) | 
						
							| 27 |  | oveq1 |  |-  ( k = 1 -> ( k + 1 ) = ( 1 + 1 ) ) | 
						
							| 28 |  | 1p1e2 |  |-  ( 1 + 1 ) = 2 | 
						
							| 29 | 27 28 | eqtrdi |  |-  ( k = 1 -> ( k + 1 ) = 2 ) | 
						
							| 30 | 29 | fveq2d |  |-  ( k = 1 -> ( P ` ( k + 1 ) ) = ( P ` 2 ) ) | 
						
							| 31 | 26 30 | preq12d |  |-  ( k = 1 -> { ( P ` k ) , ( P ` ( k + 1 ) ) } = { ( P ` 1 ) , ( P ` 2 ) } ) | 
						
							| 32 |  | 2fveq3 |  |-  ( k = 1 -> ( I ` ( F ` k ) ) = ( I ` ( F ` 1 ) ) ) | 
						
							| 33 | 31 32 | sseq12d |  |-  ( k = 1 -> ( { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) <-> { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) ) ) | 
						
							| 34 | 19 20 25 33 | ralpr |  |-  ( A. k e. { 0 , 1 } { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) <-> ( { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) /\ { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) ) ) | 
						
							| 35 | 18 34 | bitri |  |-  ( A. k e. ( 0 ..^ ( # ` F ) ) { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) <-> ( { ( P ` 0 ) , ( P ` 1 ) } C_ ( I ` ( F ` 0 ) ) /\ { ( P ` 1 ) , ( P ` 2 ) } C_ ( I ` ( F ` 1 ) ) ) ) | 
						
							| 36 | 16 35 | sylibr |  |-  ( ph -> A. k e. ( 0 ..^ ( # ` F ) ) { ( P ` k ) , ( P ` ( k + 1 ) ) } C_ ( I ` ( F ` k ) ) ) |