| Step | Hyp | Ref
 | Expression | 
| 1 |   | fveq2 5558 | 
. . . . . 6
⊢ (𝑦 = 𝐷 → (𝐹‘𝑦) = (𝐹‘𝐷)) | 
| 2 | 1 | sseq1d 3212 | 
. . . . 5
⊢ (𝑦 = 𝐷 → ((𝐹‘𝑦) ⊆ 𝐶 ↔ (𝐹‘𝐷) ⊆ 𝐶)) | 
| 3 | 2 | imbi2d 230 | 
. . . 4
⊢ (𝑦 = 𝐷 → ((∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑦) ⊆ 𝐶) ↔ (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝐷) ⊆ 𝐶))) | 
| 4 |   | nfrab1 2677 | 
. . . . . . 7
⊢
Ⅎ𝑥{𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} | 
| 5 | 4 | nfcri 2333 | 
. . . . . 6
⊢
Ⅎ𝑥 𝑦 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} | 
| 6 |   | nfra1 2528 | 
. . . . . . 7
⊢
Ⅎ𝑥∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 | 
| 7 |   | fvmpt2.1 | 
. . . . . . . . . 10
⊢ 𝐹 = (𝑥 ∈ 𝐴 ↦ 𝐵) | 
| 8 |   | nfmpt1 4126 | 
. . . . . . . . . 10
⊢
Ⅎ𝑥(𝑥 ∈ 𝐴 ↦ 𝐵) | 
| 9 | 7, 8 | nfcxfr 2336 | 
. . . . . . . . 9
⊢
Ⅎ𝑥𝐹 | 
| 10 |   | nfcv 2339 | 
. . . . . . . . 9
⊢
Ⅎ𝑥𝑦 | 
| 11 | 9, 10 | nffv 5568 | 
. . . . . . . 8
⊢
Ⅎ𝑥(𝐹‘𝑦) | 
| 12 |   | nfcv 2339 | 
. . . . . . . 8
⊢
Ⅎ𝑥𝐶 | 
| 13 | 11, 12 | nfss 3176 | 
. . . . . . 7
⊢
Ⅎ𝑥(𝐹‘𝑦) ⊆ 𝐶 | 
| 14 | 6, 13 | nfim 1586 | 
. . . . . 6
⊢
Ⅎ𝑥(∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑦) ⊆ 𝐶) | 
| 15 | 5, 14 | nfim 1586 | 
. . . . 5
⊢
Ⅎ𝑥(𝑦 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑦) ⊆ 𝐶)) | 
| 16 |   | eleq1 2259 | 
. . . . . 6
⊢ (𝑥 = 𝑦 → (𝑥 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} ↔ 𝑦 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V})) | 
| 17 |   | fveq2 5558 | 
. . . . . . . 8
⊢ (𝑥 = 𝑦 → (𝐹‘𝑥) = (𝐹‘𝑦)) | 
| 18 | 17 | sseq1d 3212 | 
. . . . . . 7
⊢ (𝑥 = 𝑦 → ((𝐹‘𝑥) ⊆ 𝐶 ↔ (𝐹‘𝑦) ⊆ 𝐶)) | 
| 19 | 18 | imbi2d 230 | 
. . . . . 6
⊢ (𝑥 = 𝑦 → ((∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑥) ⊆ 𝐶) ↔ (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑦) ⊆ 𝐶))) | 
| 20 | 16, 19 | imbi12d 234 | 
. . . . 5
⊢ (𝑥 = 𝑦 → ((𝑥 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑥) ⊆ 𝐶)) ↔ (𝑦 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑦) ⊆ 𝐶)))) | 
| 21 | 7 | dmmpt 5165 | 
. . . . . . 7
⊢ dom 𝐹 = {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} | 
| 22 | 21 | eleq2i 2263 | 
. . . . . 6
⊢ (𝑥 ∈ dom 𝐹 ↔ 𝑥 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V}) | 
| 23 | 21 | rabeq2i 2760 | 
. . . . . . . . . 10
⊢ (𝑥 ∈ dom 𝐹 ↔ (𝑥 ∈ 𝐴 ∧ 𝐵 ∈ V)) | 
| 24 | 7 | fvmpt2 5645 | 
. . . . . . . . . . 11
⊢ ((𝑥 ∈ 𝐴 ∧ 𝐵 ∈ V) → (𝐹‘𝑥) = 𝐵) | 
| 25 |   | eqimss 3237 | 
. . . . . . . . . . 11
⊢ ((𝐹‘𝑥) = 𝐵 → (𝐹‘𝑥) ⊆ 𝐵) | 
| 26 | 24, 25 | syl 14 | 
. . . . . . . . . 10
⊢ ((𝑥 ∈ 𝐴 ∧ 𝐵 ∈ V) → (𝐹‘𝑥) ⊆ 𝐵) | 
| 27 | 23, 26 | sylbi 121 | 
. . . . . . . . 9
⊢ (𝑥 ∈ dom 𝐹 → (𝐹‘𝑥) ⊆ 𝐵) | 
| 28 | 27 | adantr 276 | 
. . . . . . . 8
⊢ ((𝑥 ∈ dom 𝐹 ∧ ∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶) → (𝐹‘𝑥) ⊆ 𝐵) | 
| 29 | 7 | dmmptss 5166 | 
. . . . . . . . . 10
⊢ dom 𝐹 ⊆ 𝐴 | 
| 30 | 29 | sseli 3179 | 
. . . . . . . . 9
⊢ (𝑥 ∈ dom 𝐹 → 𝑥 ∈ 𝐴) | 
| 31 |   | rsp 2544 | 
. . . . . . . . 9
⊢
(∀𝑥 ∈
𝐴 𝐵 ⊆ 𝐶 → (𝑥 ∈ 𝐴 → 𝐵 ⊆ 𝐶)) | 
| 32 | 30, 31 | mpan9 281 | 
. . . . . . . 8
⊢ ((𝑥 ∈ dom 𝐹 ∧ ∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶) → 𝐵 ⊆ 𝐶) | 
| 33 | 28, 32 | sstrd 3193 | 
. . . . . . 7
⊢ ((𝑥 ∈ dom 𝐹 ∧ ∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶) → (𝐹‘𝑥) ⊆ 𝐶) | 
| 34 | 33 | ex 115 | 
. . . . . 6
⊢ (𝑥 ∈ dom 𝐹 → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑥) ⊆ 𝐶)) | 
| 35 | 22, 34 | sylbir 135 | 
. . . . 5
⊢ (𝑥 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑥) ⊆ 𝐶)) | 
| 36 | 15, 20, 35 | chvar 1771 | 
. . . 4
⊢ (𝑦 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝑦) ⊆ 𝐶)) | 
| 37 | 3, 36 | vtoclga 2830 | 
. . 3
⊢ (𝐷 ∈ {𝑥 ∈ 𝐴 ∣ 𝐵 ∈ V} → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝐷) ⊆ 𝐶)) | 
| 38 | 37, 21 | eleq2s 2291 | 
. 2
⊢ (𝐷 ∈ dom 𝐹 → (∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶 → (𝐹‘𝐷) ⊆ 𝐶)) | 
| 39 | 38 | imp 124 | 
1
⊢ ((𝐷 ∈ dom 𝐹 ∧ ∀𝑥 ∈ 𝐴 𝐵 ⊆ 𝐶) → (𝐹‘𝐷) ⊆ 𝐶) |