| Step | Hyp | Ref
 | Expression | 
| 1 |   | df-rex 2481 | 
. . . 4
⊢
(∃𝑥 ∈
𝐴 (𝐹‘𝑥) = 𝐵 ↔ ∃𝑥(𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵)) | 
| 2 |   | 19.41v 1917 | 
. . . . 5
⊢
(∃𝑥((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) ↔ (∃𝑥(𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴)) | 
| 3 |   | simpl 109 | 
. . . . . . . . . 10
⊢ ((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) → 𝑥 ∈ 𝐴) | 
| 4 | 3 | anim1i 340 | 
. . . . . . . . 9
⊢ (((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → (𝑥 ∈ 𝐴 ∧ 𝐹 Fn 𝐴)) | 
| 5 | 4 | ancomd 267 | 
. . . . . . . 8
⊢ (((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → (𝐹 Fn 𝐴 ∧ 𝑥 ∈ 𝐴)) | 
| 6 |   | funfvex 5575 | 
. . . . . . . . 9
⊢ ((Fun
𝐹 ∧ 𝑥 ∈ dom 𝐹) → (𝐹‘𝑥) ∈ V) | 
| 7 | 6 | funfni 5358 | 
. . . . . . . 8
⊢ ((𝐹 Fn 𝐴 ∧ 𝑥 ∈ 𝐴) → (𝐹‘𝑥) ∈ V) | 
| 8 | 5, 7 | syl 14 | 
. . . . . . 7
⊢ (((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → (𝐹‘𝑥) ∈ V) | 
| 9 |   | simpr 110 | 
. . . . . . . . 9
⊢ ((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) → (𝐹‘𝑥) = 𝐵) | 
| 10 | 9 | eleq1d 2265 | 
. . . . . . . 8
⊢ ((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) → ((𝐹‘𝑥) ∈ V ↔ 𝐵 ∈ V)) | 
| 11 | 10 | adantr 276 | 
. . . . . . 7
⊢ (((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → ((𝐹‘𝑥) ∈ V ↔ 𝐵 ∈ V)) | 
| 12 | 8, 11 | mpbid 147 | 
. . . . . 6
⊢ (((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → 𝐵 ∈ V) | 
| 13 | 12 | exlimiv 1612 | 
. . . . 5
⊢
(∃𝑥((𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → 𝐵 ∈ V) | 
| 14 | 2, 13 | sylbir 135 | 
. . . 4
⊢
((∃𝑥(𝑥 ∈ 𝐴 ∧ (𝐹‘𝑥) = 𝐵) ∧ 𝐹 Fn 𝐴) → 𝐵 ∈ V) | 
| 15 | 1, 14 | sylanb 284 | 
. . 3
⊢
((∃𝑥 ∈
𝐴 (𝐹‘𝑥) = 𝐵 ∧ 𝐹 Fn 𝐴) → 𝐵 ∈ V) | 
| 16 | 15 | expcom 116 | 
. 2
⊢ (𝐹 Fn 𝐴 → (∃𝑥 ∈ 𝐴 (𝐹‘𝑥) = 𝐵 → 𝐵 ∈ V)) | 
| 17 |   | fnrnfv 5607 | 
. . . 4
⊢ (𝐹 Fn 𝐴 → ran 𝐹 = {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = (𝐹‘𝑥)}) | 
| 18 | 17 | eleq2d 2266 | 
. . 3
⊢ (𝐹 Fn 𝐴 → (𝐵 ∈ ran 𝐹 ↔ 𝐵 ∈ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = (𝐹‘𝑥)})) | 
| 19 |   | eqeq1 2203 | 
. . . . . 6
⊢ (𝑦 = 𝐵 → (𝑦 = (𝐹‘𝑥) ↔ 𝐵 = (𝐹‘𝑥))) | 
| 20 |   | eqcom 2198 | 
. . . . . 6
⊢ (𝐵 = (𝐹‘𝑥) ↔ (𝐹‘𝑥) = 𝐵) | 
| 21 | 19, 20 | bitrdi 196 | 
. . . . 5
⊢ (𝑦 = 𝐵 → (𝑦 = (𝐹‘𝑥) ↔ (𝐹‘𝑥) = 𝐵)) | 
| 22 | 21 | rexbidv 2498 | 
. . . 4
⊢ (𝑦 = 𝐵 → (∃𝑥 ∈ 𝐴 𝑦 = (𝐹‘𝑥) ↔ ∃𝑥 ∈ 𝐴 (𝐹‘𝑥) = 𝐵)) | 
| 23 | 22 | elab3g 2915 | 
. . 3
⊢
((∃𝑥 ∈
𝐴 (𝐹‘𝑥) = 𝐵 → 𝐵 ∈ V) → (𝐵 ∈ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = (𝐹‘𝑥)} ↔ ∃𝑥 ∈ 𝐴 (𝐹‘𝑥) = 𝐵)) | 
| 24 | 18, 23 | sylan9bbr 463 | 
. 2
⊢
(((∃𝑥 ∈
𝐴 (𝐹‘𝑥) = 𝐵 → 𝐵 ∈ V) ∧ 𝐹 Fn 𝐴) → (𝐵 ∈ ran 𝐹 ↔ ∃𝑥 ∈ 𝐴 (𝐹‘𝑥) = 𝐵)) | 
| 25 | 16, 24 | mpancom 422 | 
1
⊢ (𝐹 Fn 𝐴 → (𝐵 ∈ ran 𝐹 ↔ ∃𝑥 ∈ 𝐴 (𝐹‘𝑥) = 𝐵)) |