| Step | Hyp | Ref
 | Expression | 
| 1 |   | ssel2 3269 | 
. . . . . . . 8
⊢ ((C ⊆ A ∧ y ∈ C) → y
∈ A) | 
| 2 | 1 | anim1i 551 | 
. . . . . . 7
⊢ (((C ⊆ A ∧ y ∈ C) ∧ D ∈ A) → (y
∈ A ∧ D ∈ A)) | 
| 3 | 2 | an32s 779 | 
. . . . . 6
⊢ (((C ⊆ A ∧ D ∈ A) ∧ y ∈ C) → (y
∈ A ∧ D ∈ A)) | 
| 4 |   | isorel 5490 | 
. . . . . . 7
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → (yRD ↔ (H
‘y)S(H
‘D))) | 
| 5 |   | fvex 5340 | 
. . . . . . . . 9
⊢ (H ‘y)
∈ V | 
| 6 |   | breq1 4643 | 
. . . . . . . . 9
⊢ (x = (H
‘y) → (xS(H ‘D)
↔ (H ‘y)S(H ‘D))) | 
| 7 | 5, 6 | ceqsexv 2895 | 
. . . . . . . 8
⊢ (∃x(x = (H
‘y) ∧ xS(H
‘D)) ↔ (H ‘y)S(H ‘D)) | 
| 8 |   | eqcom 2355 | 
. . . . . . . . . . 11
⊢ (x = (H
‘y) ↔ (H ‘y) =
x) | 
| 9 |   | isof1o 5489 | 
. . . . . . . . . . . . 13
⊢ (H Isom R,
S (A,
B) → H:A–1-1-onto→B) | 
| 10 |   | f1ofn 5289 | 
. . . . . . . . . . . . 13
⊢ (H:A–1-1-onto→B →
H Fn A) | 
| 11 | 9, 10 | syl 15 | 
. . . . . . . . . . . 12
⊢ (H Isom R,
S (A,
B) → H Fn A) | 
| 12 |   | simpl 443 | 
. . . . . . . . . . . 12
⊢ ((y ∈ A ∧ D ∈ A) → y
∈ A) | 
| 13 |   | fnbrfvb 5359 | 
. . . . . . . . . . . 12
⊢ ((H Fn A ∧ y ∈ A) →
((H ‘y) = x ↔
yHx)) | 
| 14 | 11, 12, 13 | syl2an 463 | 
. . . . . . . . . . 11
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → ((H ‘y) =
x ↔ yHx)) | 
| 15 | 8, 14 | syl5bb 248 | 
. . . . . . . . . 10
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → (x = (H
‘y) ↔ yHx)) | 
| 16 | 15 | anbi1d 685 | 
. . . . . . . . 9
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → ((x = (H
‘y) ∧ xS(H
‘D)) ↔ (yHx ∧ xS(H ‘D)))) | 
| 17 | 16 | exbidv 1626 | 
. . . . . . . 8
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → (∃x(x = (H
‘y) ∧ xS(H
‘D)) ↔ ∃x(yHx ∧ xS(H ‘D)))) | 
| 18 | 7, 17 | syl5bbr 250 | 
. . . . . . 7
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → ((H ‘y)S(H ‘D)
↔ ∃x(yHx ∧ xS(H
‘D)))) | 
| 19 | 4, 18 | bitrd 244 | 
. . . . . 6
⊢ ((H Isom R,
S (A,
B) ∧
(y ∈
A ∧
D ∈
A)) → (yRD ↔ ∃x(yHx ∧ xS(H ‘D)))) | 
| 20 | 3, 19 | sylan2 460 | 
. . . . 5
⊢ ((H Isom R,
S (A,
B) ∧
((C ⊆
A ∧
D ∈
A) ∧
y ∈
C)) → (yRD ↔ ∃x(yHx ∧ xS(H ‘D)))) | 
| 21 | 20 | anassrs 629 | 
. . . 4
⊢ (((H Isom R,
S (A,
B) ∧
(C ⊆
A ∧
D ∈
A)) ∧
y ∈
C) → (yRD ↔ ∃x(yHx ∧ xS(H ‘D)))) | 
| 22 | 21 | rexbidva 2632 | 
. . 3
⊢ ((H Isom R,
S (A,
B) ∧
(C ⊆
A ∧
D ∈
A)) → (∃y ∈ C yRD ↔ ∃y ∈ C ∃x(yHx ∧ xS(H ‘D)))) | 
| 23 |   | elin 3220 | 
. . . . . 6
⊢ (y ∈ (C ∩ (◡R
“ {D})) ↔ (y ∈ C ∧ y ∈ (◡R
“ {D}))) | 
| 24 |   | eliniseg 5021 | 
. . . . . . 7
⊢ (y ∈ (◡R
“ {D}) ↔ yRD) | 
| 25 | 24 | anbi2i 675 | 
. . . . . 6
⊢ ((y ∈ C ∧ y ∈ (◡R
“ {D})) ↔ (y ∈ C ∧ yRD)) | 
| 26 | 23, 25 | bitri 240 | 
. . . . 5
⊢ (y ∈ (C ∩ (◡R
“ {D})) ↔ (y ∈ C ∧ yRD)) | 
| 27 | 26 | exbii 1582 | 
. . . 4
⊢ (∃y y ∈ (C ∩ (◡R
“ {D})) ↔ ∃y(y ∈ C ∧ yRD)) | 
| 28 |   | neq0 3561 | 
. . . 4
⊢ (¬ (C ∩ (◡R
“ {D})) = ∅ ↔ ∃y y ∈ (C ∩ (◡R
“ {D}))) | 
| 29 |   | df-rex 2621 | 
. . . 4
⊢ (∃y ∈ C yRD ↔ ∃y(y ∈ C ∧ yRD)) | 
| 30 | 27, 28, 29 | 3bitr4i 268 | 
. . 3
⊢ (¬ (C ∩ (◡R
“ {D})) = ∅ ↔ ∃y ∈ C yRD) | 
| 31 |   | elima 4755 | 
. . . . . . 7
⊢ (x ∈ (H “ C)
↔ ∃y ∈ C yHx) | 
| 32 |   | eliniseg 5021 | 
. . . . . . 7
⊢ (x ∈ (◡S
“ {(H ‘D)}) ↔ xS(H ‘D)) | 
| 33 | 31, 32 | anbi12i 678 | 
. . . . . 6
⊢ ((x ∈ (H “ C)
∧ x ∈ (◡S
“ {(H ‘D)})) ↔ (∃y ∈ C yHx ∧ xS(H ‘D))) | 
| 34 |   | elin 3220 | 
. . . . . 6
⊢ (x ∈ ((H “ C)
∩ (◡S “ {(H
‘D)})) ↔ (x ∈ (H “ C)
∧ x ∈ (◡S
“ {(H ‘D)}))) | 
| 35 |   | r19.41v 2765 | 
. . . . . 6
⊢ (∃y ∈ C (yHx ∧ xS(H ‘D))
↔ (∃y ∈ C yHx ∧ xS(H
‘D))) | 
| 36 | 33, 34, 35 | 3bitr4i 268 | 
. . . . 5
⊢ (x ∈ ((H “ C)
∩ (◡S “ {(H
‘D)})) ↔ ∃y ∈ C (yHx ∧ xS(H ‘D))) | 
| 37 | 36 | exbii 1582 | 
. . . 4
⊢ (∃x x ∈ ((H “ C)
∩ (◡S “ {(H
‘D)})) ↔ ∃x∃y ∈ C (yHx ∧ xS(H ‘D))) | 
| 38 |   | neq0 3561 | 
. . . 4
⊢ (¬ ((H “ C)
∩ (◡S “ {(H
‘D)})) = ∅ ↔ ∃x x ∈ ((H “ C)
∩ (◡S “ {(H
‘D)}))) | 
| 39 |   | rexcom4 2879 | 
. . . 4
⊢ (∃y ∈ C ∃x(yHx ∧ xS(H ‘D))
↔ ∃x∃y ∈ C (yHx ∧ xS(H
‘D))) | 
| 40 | 37, 38, 39 | 3bitr4i 268 | 
. . 3
⊢ (¬ ((H “ C)
∩ (◡S “ {(H
‘D)})) = ∅ ↔ ∃y ∈ C ∃x(yHx ∧ xS(H ‘D))) | 
| 41 | 22, 30, 40 | 3bitr4g 279 | 
. 2
⊢ ((H Isom R,
S (A,
B) ∧
(C ⊆
A ∧
D ∈
A)) → (¬ (C ∩ (◡R
“ {D})) = ∅ ↔ ¬ ((H “ C)
∩ (◡S “ {(H
‘D)})) = ∅)) | 
| 42 | 41 | con4bid 284 | 
1
⊢ ((H Isom R,
S (A,
B) ∧
(C ⊆
A ∧
D ∈
A)) → ((C ∩ (◡R
“ {D})) = ∅ ↔ ((H
“ C) ∩ (◡S
“ {(H ‘D)})) = ∅)) |