| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dlwwlknondlwlknonbij.v | ⊢ 𝑉  =  ( Vtx ‘ 𝐺 ) | 
						
							| 2 |  | dlwwlknondlwlknonbij.w | ⊢ 𝑊  =  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) } | 
						
							| 3 |  | dlwwlknondlwlknonbij.d | ⊢ 𝐷  =  { 𝑤  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑤 ‘ ( 𝑁  −  2 ) )  =  𝑋 } | 
						
							| 4 |  | dlwwlknondlwlknonf1o.f | ⊢ 𝐹  =  ( 𝑐  ∈  𝑊  ↦  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ) | 
						
							| 5 |  | df-3an | ⊢ ( ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 )  ↔  ( ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 )  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) ) | 
						
							| 6 | 5 | rabbii | ⊢ { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) }  =  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 )  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) } | 
						
							| 7 | 2 6 | eqtri | ⊢ 𝑊  =  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 )  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) } | 
						
							| 8 |  | eqid | ⊢ { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  =  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) } | 
						
							| 9 |  | eqid | ⊢ ( 𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ↦  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) )  =  ( 𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ↦  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ) | 
						
							| 10 |  | eluz2nn | ⊢ ( 𝑁  ∈  ( ℤ≥ ‘ 2 )  →  𝑁  ∈  ℕ ) | 
						
							| 11 | 1 8 9 | clwwlknonclwlknonf1o | ⊢ ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ℕ )  →  ( 𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ↦  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ) : { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) } –1-1-onto→ ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 ) ) | 
						
							| 12 | 10 11 | syl3an3 | ⊢ ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  →  ( 𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ↦  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ) : { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) } –1-1-onto→ ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 ) ) | 
						
							| 13 |  | fveq1 | ⊢ ( 𝑦  =  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) )  →  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  ( ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 14 | 13 | 3ad2ant3 | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ∧  𝑦  =  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) )  →  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  ( ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 15 |  | 2fveq3 | ⊢ ( 𝑤  =  𝑐  →  ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) | 
						
							| 16 | 15 | eqeq1d | ⊢ ( 𝑤  =  𝑐  →  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ↔  ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁 ) ) | 
						
							| 17 |  | fveq2 | ⊢ ( 𝑤  =  𝑐  →  ( 2nd  ‘ 𝑤 )  =  ( 2nd  ‘ 𝑐 ) ) | 
						
							| 18 | 17 | fveq1d | ⊢ ( 𝑤  =  𝑐  →  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  ( ( 2nd  ‘ 𝑐 ) ‘ 0 ) ) | 
						
							| 19 | 18 | eqeq1d | ⊢ ( 𝑤  =  𝑐  →  ( ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋  ↔  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) ) | 
						
							| 20 | 16 19 | anbi12d | ⊢ ( 𝑤  =  𝑐  →  ( ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 )  ↔  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) ) ) | 
						
							| 21 | 20 | elrab | ⊢ ( 𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ↔  ( 𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) ) ) | 
						
							| 22 |  | simplrl | ⊢ ( ( ( 𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) )  ∧  ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) )  →  ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁 ) | 
						
							| 23 |  | simpll | ⊢ ( ( ( 𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) )  ∧  ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) )  →  𝑐  ∈  ( ClWalks ‘ 𝐺 ) ) | 
						
							| 24 |  | simpr3 | ⊢ ( ( ( 𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) )  ∧  ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) )  →  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) | 
						
							| 25 | 22 23 24 | 3jca | ⊢ ( ( ( 𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) )  ∧  ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) )  →  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) ) | 
						
							| 26 | 25 | ex | ⊢ ( ( 𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑐 ) ‘ 0 )  =  𝑋 ) )  →  ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  →  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) ) ) | 
						
							| 27 | 21 26 | sylbi | ⊢ ( 𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  →  ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  →  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) ) ) | 
						
							| 28 | 27 | impcom | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) } )  →  ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) ) ) | 
						
							| 29 |  | dlwwlknondlwlknonf1olem1 | ⊢ ( ( ( ♯ ‘ ( 1st  ‘ 𝑐 ) )  =  𝑁  ∧  𝑐  ∈  ( ClWalks ‘ 𝐺 )  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  →  ( ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ‘ ( 𝑁  −  2 ) )  =  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 30 | 28 29 | syl | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) } )  →  ( ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ‘ ( 𝑁  −  2 ) )  =  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 31 | 30 | 3adant3 | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ∧  𝑦  =  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) )  →  ( ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) ‘ ( 𝑁  −  2 ) )  =  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 32 | 14 31 | eqtrd | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ∧  𝑦  =  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) )  →  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 33 | 32 | eqeq1d | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ∧  𝑦  =  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) )  →  ( ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋  ↔  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) ) | 
						
							| 34 |  | nfv | ⊢ Ⅎ 𝑤 ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 | 
						
							| 35 | 17 | fveq1d | ⊢ ( 𝑤  =  𝑐  →  ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 36 | 35 | eqeq1d | ⊢ ( 𝑤  =  𝑐  →  ( ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋  ↔  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) ) | 
						
							| 37 | 34 36 | sbiev | ⊢ ( [ 𝑐  /  𝑤 ] ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋  ↔  ( ( 2nd  ‘ 𝑐 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) | 
						
							| 38 | 33 37 | bitr4di | ⊢ ( ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  ∧  𝑐  ∈  { 𝑤  ∈  ( ClWalks ‘ 𝐺 )  ∣  ( ( ♯ ‘ ( 1st  ‘ 𝑤 ) )  =  𝑁  ∧  ( ( 2nd  ‘ 𝑤 ) ‘ 0 )  =  𝑋 ) }  ∧  𝑦  =  ( ( 2nd  ‘ 𝑐 )  prefix  ( ♯ ‘ ( 1st  ‘ 𝑐 ) ) ) )  →  ( ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋  ↔  [ 𝑐  /  𝑤 ] ( ( 2nd  ‘ 𝑤 ) ‘ ( 𝑁  −  2 ) )  =  𝑋 ) ) | 
						
							| 39 | 7 8 4 9 12 38 | f1ossf1o | ⊢ ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  →  𝐹 : 𝑊 –1-1-onto→ { 𝑦  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 } ) | 
						
							| 40 |  | fveq1 | ⊢ ( 𝑤  =  𝑦  →  ( 𝑤 ‘ ( 𝑁  −  2 ) )  =  ( 𝑦 ‘ ( 𝑁  −  2 ) ) ) | 
						
							| 41 | 40 | eqeq1d | ⊢ ( 𝑤  =  𝑦  →  ( ( 𝑤 ‘ ( 𝑁  −  2 ) )  =  𝑋  ↔  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 ) ) | 
						
							| 42 | 41 | cbvrabv | ⊢ { 𝑤  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑤 ‘ ( 𝑁  −  2 ) )  =  𝑋 }  =  { 𝑦  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 } | 
						
							| 43 | 3 42 | eqtri | ⊢ 𝐷  =  { 𝑦  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 } | 
						
							| 44 |  | f1oeq3 | ⊢ ( 𝐷  =  { 𝑦  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 }  →  ( 𝐹 : 𝑊 –1-1-onto→ 𝐷  ↔  𝐹 : 𝑊 –1-1-onto→ { 𝑦  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 } ) ) | 
						
							| 45 | 43 44 | ax-mp | ⊢ ( 𝐹 : 𝑊 –1-1-onto→ 𝐷  ↔  𝐹 : 𝑊 –1-1-onto→ { 𝑦  ∈  ( 𝑋 ( ClWWalksNOn ‘ 𝐺 ) 𝑁 )  ∣  ( 𝑦 ‘ ( 𝑁  −  2 ) )  =  𝑋 } ) | 
						
							| 46 | 39 45 | sylibr | ⊢ ( ( 𝐺  ∈  USPGraph  ∧  𝑋  ∈  𝑉  ∧  𝑁  ∈  ( ℤ≥ ‘ 2 ) )  →  𝐹 : 𝑊 –1-1-onto→ 𝐷 ) |