| Step | Hyp | Ref | Expression | 
						
							| 1 |  | 2wlkd.p | ⊢ 𝑃  =  〈“ 𝐴 𝐵 𝐶 ”〉 | 
						
							| 2 |  | 2wlkd.f | ⊢ 𝐹  =  〈“ 𝐽 𝐾 ”〉 | 
						
							| 3 |  | 2wlkd.s | ⊢ ( 𝜑  →  ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) ) | 
						
							| 4 |  | 2wlkd.n | ⊢ ( 𝜑  →  ( 𝐴  ≠  𝐵  ∧  𝐵  ≠  𝐶 ) ) | 
						
							| 5 |  | 2wlkd.e | ⊢ ( 𝜑  →  ( { 𝐴 ,  𝐵 }  ⊆  ( 𝐼 ‘ 𝐽 )  ∧  { 𝐵 ,  𝐶 }  ⊆  ( 𝐼 ‘ 𝐾 ) ) ) | 
						
							| 6 | 1 2 3 4 5 | 2wlkdlem9 | ⊢ ( 𝜑  →  ( { 𝐴 ,  𝐵 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { 𝐵 ,  𝐶 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) | 
						
							| 7 | 1 2 3 | 2wlkdlem3 | ⊢ ( 𝜑  →  ( ( 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 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ↔  { 𝐴 ,  𝐵 }  ⊆  ( 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 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) )  ↔  { 𝐵 ,  𝐶 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) | 
						
							| 14 | 10 13 | anbi12d | ⊢ ( ( ( 𝑃 ‘ 0 )  =  𝐴  ∧  ( 𝑃 ‘ 1 )  =  𝐵  ∧  ( 𝑃 ‘ 2 )  =  𝐶 )  →  ( ( { ( 𝑃 ‘ 0 ) ,  ( 𝑃 ‘ 1 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { ( 𝑃 ‘ 1 ) ,  ( 𝑃 ‘ 2 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) )  ↔  ( { 𝐴 ,  𝐵 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { 𝐵 ,  𝐶 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) ) | 
						
							| 15 | 7 14 | syl | ⊢ ( 𝜑  →  ( ( { ( 𝑃 ‘ 0 ) ,  ( 𝑃 ‘ 1 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { ( 𝑃 ‘ 1 ) ,  ( 𝑃 ‘ 2 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) )  ↔  ( { 𝐴 ,  𝐵 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { 𝐵 ,  𝐶 }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) ) | 
						
							| 16 | 6 15 | mpbird | ⊢ ( 𝜑  →  ( { ( 𝑃 ‘ 0 ) ,  ( 𝑃 ‘ 1 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { ( 𝑃 ‘ 1 ) ,  ( 𝑃 ‘ 2 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) | 
						
							| 17 | 1 2 | 2wlkdlem2 | ⊢ ( 0 ..^ ( ♯ ‘ 𝐹 ) )  =  { 0 ,  1 } | 
						
							| 18 | 17 | raleqi | ⊢ ( ∀ 𝑘  ∈  ( 0 ..^ ( ♯ ‘ 𝐹 ) ) { ( 𝑃 ‘ 𝑘 ) ,  ( 𝑃 ‘ ( 𝑘  +  1 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) )  ↔  ∀ 𝑘  ∈  { 0 ,  1 } { ( 𝑃 ‘ 𝑘 ) ,  ( 𝑃 ‘ ( 𝑘  +  1 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) ) ) | 
						
							| 19 |  | c0ex | ⊢ 0  ∈  V | 
						
							| 20 |  | 1ex | ⊢ 1  ∈  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 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) )  ↔  { ( 𝑃 ‘ 0 ) ,  ( 𝑃 ‘ 1 ) }  ⊆  ( 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 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) )  ↔  { ( 𝑃 ‘ 1 ) ,  ( 𝑃 ‘ 2 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) | 
						
							| 34 | 19 20 25 33 | ralpr | ⊢ ( ∀ 𝑘  ∈  { 0 ,  1 } { ( 𝑃 ‘ 𝑘 ) ,  ( 𝑃 ‘ ( 𝑘  +  1 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) )  ↔  ( { ( 𝑃 ‘ 0 ) ,  ( 𝑃 ‘ 1 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { ( 𝑃 ‘ 1 ) ,  ( 𝑃 ‘ 2 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) | 
						
							| 35 | 18 34 | bitri | ⊢ ( ∀ 𝑘  ∈  ( 0 ..^ ( ♯ ‘ 𝐹 ) ) { ( 𝑃 ‘ 𝑘 ) ,  ( 𝑃 ‘ ( 𝑘  +  1 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) )  ↔  ( { ( 𝑃 ‘ 0 ) ,  ( 𝑃 ‘ 1 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 0 ) )  ∧  { ( 𝑃 ‘ 1 ) ,  ( 𝑃 ‘ 2 ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 1 ) ) ) ) | 
						
							| 36 | 16 35 | sylibr | ⊢ ( 𝜑  →  ∀ 𝑘  ∈  ( 0 ..^ ( ♯ ‘ 𝐹 ) ) { ( 𝑃 ‘ 𝑘 ) ,  ( 𝑃 ‘ ( 𝑘  +  1 ) ) }  ⊆  ( 𝐼 ‘ ( 𝐹 ‘ 𝑘 ) ) ) |