| Step | Hyp | Ref
 | Expression | 
| 1 |   | df-sfin 4447 | 
. . . . . . 7
⊢ ( Sfin (N,
P) ↔ (N ∈ Nn ∧ P ∈ Nn ∧ ∃a(℘1a ∈ N ∧ ℘a ∈ P))) | 
| 2 | 1 | simp2bi 971 | 
. . . . . 6
⊢ ( Sfin (N,
P) → P ∈ Nn ) | 
| 3 | 2 | adantl 452 | 
. . . . 5
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → P ∈ Nn ) | 
| 4 |   | ltfinirr 4458 | 
. . . . 5
⊢ (P ∈ Nn → ¬ ⟪P, P⟫
∈ <fin ) | 
| 5 | 3, 4 | syl 15 | 
. . . 4
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → ¬ ⟪P, P⟫
∈ <fin ) | 
| 6 |   | sfinltfin 4536 | 
. . . 4
⊢ ((( Sfin (M,
P) ∧ Sfin (N,
P)) ∧
⟪M, N⟫ ∈
<fin ) → ⟪P,
P⟫ ∈ <fin ) | 
| 7 | 5, 6 | mtand 640 | 
. . 3
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → ¬ ⟪M, N⟫
∈ <fin ) | 
| 8 |   | sfinltfin 4536 | 
. . . . . 6
⊢ ((( Sfin (N,
P) ∧ Sfin (M,
P)) ∧
⟪N, M⟫ ∈
<fin ) → ⟪P,
P⟫ ∈ <fin ) | 
| 9 | 8 | ex 423 | 
. . . . 5
⊢ (( Sfin (N,
P) ∧ Sfin (M,
P)) → (⟪N, M⟫
∈ <fin → ⟪P, P⟫
∈ <fin )) | 
| 10 | 9 | ancoms 439 | 
. . . 4
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → (⟪N, M⟫
∈ <fin → ⟪P, P⟫
∈ <fin )) | 
| 11 | 5, 10 | mtod 168 | 
. . 3
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → ¬ ⟪N, M⟫
∈ <fin ) | 
| 12 |   | ioran 476 | 
. . 3
⊢ (¬
(⟪M, N⟫ ∈
<fin  ∨ ⟪N, M⟫
∈ <fin ) ↔ (¬
⟪M, N⟫ ∈
<fin ∧ ¬ ⟪N, M⟫
∈ <fin )) | 
| 13 | 7, 11, 12 | sylanbrc 645 | 
. 2
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → ¬ (⟪M, N⟫
∈ <fin 
∨ ⟪N, M⟫ ∈
<fin )) | 
| 14 |   | df-sfin 4447 | 
. . . . . . 7
⊢ ( Sfin (M,
P) ↔ (M ∈ Nn ∧ P ∈ Nn ∧ ∃a(℘1a ∈ M ∧ ℘a ∈ P))) | 
| 15 | 14 | simp1bi 970 | 
. . . . . 6
⊢ ( Sfin (M,
P) → M ∈ Nn ) | 
| 16 | 15 | adantr 451 | 
. . . . 5
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → M ∈ Nn ) | 
| 17 | 1 | simp1bi 970 | 
. . . . . 6
⊢ ( Sfin (N,
P) → N ∈ Nn ) | 
| 18 | 17 | adantl 452 | 
. . . . 5
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → N ∈ Nn ) | 
| 19 |   | ne0i 3557 | 
. . . . . . . . . 10
⊢ (℘1a ∈ M → M ≠
∅) | 
| 20 | 19 | adantr 451 | 
. . . . . . . . 9
⊢ ((℘1a ∈ M ∧ ℘a ∈ P) →
M ≠ ∅) | 
| 21 | 20 | exlimiv 1634 | 
. . . . . . . 8
⊢ (∃a(℘1a ∈ M ∧ ℘a ∈ P) →
M ≠ ∅) | 
| 22 | 21 | 3ad2ant3 978 | 
. . . . . . 7
⊢ ((M ∈ Nn ∧ P ∈ Nn ∧ ∃a(℘1a ∈ M ∧ ℘a ∈ P)) →
M ≠ ∅) | 
| 23 | 14, 22 | sylbi 187 | 
. . . . . 6
⊢ ( Sfin (M,
P) → M ≠ ∅) | 
| 24 | 23 | adantr 451 | 
. . . . 5
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → M ≠ ∅) | 
| 25 |   | ltfintri 4467 | 
. . . . 5
⊢ ((M ∈ Nn ∧ N ∈ Nn ∧ M ≠ ∅) →
(⟪M, N⟫ ∈
<fin  ∨ M = N  ∨ ⟪N,
M⟫ ∈ <fin )) | 
| 26 | 16, 18, 24, 25 | syl3anc 1182 | 
. . . 4
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → (⟪M, N⟫
∈ <fin 
∨ M = N  ∨
⟪N, M⟫ ∈
<fin )) | 
| 27 |   | df-3or 935 | 
. . . 4
⊢ ((⟪M, N⟫
∈ <fin 
∨ M = N  ∨
⟪N, M⟫ ∈
<fin ) ↔ ((⟪M,
N⟫ ∈ <fin 
∨ M = N)  ∨
⟪N, M⟫ ∈
<fin )) | 
| 28 | 26, 27 | sylib 188 | 
. . 3
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → ((⟪M, N⟫
∈ <fin 
∨ M = N)  ∨
⟪N, M⟫ ∈
<fin )) | 
| 29 |   | or32 513 | 
. . 3
⊢ (((⟪M, N⟫
∈ <fin 
∨ M = N)  ∨
⟪N, M⟫ ∈
<fin ) ↔ ((⟪M,
N⟫ ∈ <fin 
∨ ⟪N, M⟫ ∈
<fin )  ∨ M = N)) | 
| 30 | 28, 29 | sylib 188 | 
. 2
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → ((⟪M, N⟫
∈ <fin 
∨ ⟪N, M⟫ ∈
<fin )  ∨ M = N)) | 
| 31 |   | orel1 371 | 
. 2
⊢ (¬
(⟪M, N⟫ ∈
<fin  ∨ ⟪N, M⟫
∈ <fin ) →
(((⟪M, N⟫ ∈
<fin  ∨ ⟪N, M⟫
∈ <fin ) 
∨ M = N) → M =
N)) | 
| 32 | 13, 30, 31 | sylc 56 | 
1
⊢ (( Sfin (M,
P) ∧ Sfin (N,
P)) → M = N) |