| Step | Hyp | Ref | Expression | 
|---|
| 1 |  | isumshft.5 | . . . . . . . . 9
⊢ (𝜑 → 𝑀 ∈ ℤ) | 
| 2 |  | isumshft.4 | . . . . . . . . 9
⊢ (𝜑 → 𝐾 ∈ ℤ) | 
| 3 | 1, 2 | zaddcld 12728 | . . . . . . . 8
⊢ (𝜑 → (𝑀 + 𝐾) ∈ ℤ) | 
| 4 |  | isumshft.2 | . . . . . . . . . 10
⊢ 𝑊 =
(ℤ≥‘(𝑀 + 𝐾)) | 
| 5 | 4 | eleq2i 2832 | . . . . . . . . 9
⊢ (𝑚 ∈ 𝑊 ↔ 𝑚 ∈ (ℤ≥‘(𝑀 + 𝐾))) | 
| 6 | 2 | zcnd 12725 | . . . . . . . . . . 11
⊢ (𝜑 → 𝐾 ∈ ℂ) | 
| 7 |  | eluzelcn 12891 | . . . . . . . . . . . 12
⊢ (𝑚 ∈
(ℤ≥‘(𝑀 + 𝐾)) → 𝑚 ∈ ℂ) | 
| 8 | 7, 4 | eleq2s 2858 | . . . . . . . . . . 11
⊢ (𝑚 ∈ 𝑊 → 𝑚 ∈ ℂ) | 
| 9 |  | isumshft.1 | . . . . . . . . . . . . . 14
⊢ 𝑍 =
(ℤ≥‘𝑀) | 
| 10 | 9 | fvexi 6919 | . . . . . . . . . . . . 13
⊢ 𝑍 ∈ V | 
| 11 | 10 | mptex 7244 | . . . . . . . . . . . 12
⊢ (𝑘 ∈ 𝑍 ↦ 𝐵) ∈ V | 
| 12 | 11 | shftval 15114 | . . . . . . . . . . 11
⊢ ((𝐾 ∈ ℂ ∧ 𝑚 ∈ ℂ) → (((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)‘𝑚) = ((𝑘 ∈ 𝑍 ↦ 𝐵)‘(𝑚 − 𝐾))) | 
| 13 | 6, 8, 12 | syl2an 596 | . . . . . . . . . 10
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → (((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)‘𝑚) = ((𝑘 ∈ 𝑍 ↦ 𝐵)‘(𝑚 − 𝐾))) | 
| 14 |  | simpr 484 | . . . . . . . . . . . . . . . 16
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → 𝑘 ∈ 𝑍) | 
| 15 |  | eqid 2736 | . . . . . . . . . . . . . . . . 17
⊢ (𝑘 ∈ 𝑍 ↦ 𝐵) = (𝑘 ∈ 𝑍 ↦ 𝐵) | 
| 16 | 15 | fvmpt2i 7025 | . . . . . . . . . . . . . . . 16
⊢ (𝑘 ∈ 𝑍 → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ( I ‘𝐵)) | 
| 17 | 14, 16 | syl 17 | . . . . . . . . . . . . . . 15
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ( I ‘𝐵)) | 
| 18 |  | eluzelcn 12891 | . . . . . . . . . . . . . . . . . . . 20
⊢ (𝑘 ∈
(ℤ≥‘𝑀) → 𝑘 ∈ ℂ) | 
| 19 | 18, 9 | eleq2s 2858 | . . . . . . . . . . . . . . . . . . 19
⊢ (𝑘 ∈ 𝑍 → 𝑘 ∈ ℂ) | 
| 20 |  | addcom 11448 | . . . . . . . . . . . . . . . . . . 19
⊢ ((𝐾 ∈ ℂ ∧ 𝑘 ∈ ℂ) → (𝐾 + 𝑘) = (𝑘 + 𝐾)) | 
| 21 | 6, 19, 20 | syl2an 596 | . . . . . . . . . . . . . . . . . 18
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → (𝐾 + 𝑘) = (𝑘 + 𝐾)) | 
| 22 |  | id 22 | . . . . . . . . . . . . . . . . . . . 20
⊢ (𝑘 ∈ 𝑍 → 𝑘 ∈ 𝑍) | 
| 23 | 22, 9 | eleqtrdi 2850 | . . . . . . . . . . . . . . . . . . 19
⊢ (𝑘 ∈ 𝑍 → 𝑘 ∈ (ℤ≥‘𝑀)) | 
| 24 |  | eluzadd 12908 | . . . . . . . . . . . . . . . . . . 19
⊢ ((𝑘 ∈
(ℤ≥‘𝑀) ∧ 𝐾 ∈ ℤ) → (𝑘 + 𝐾) ∈
(ℤ≥‘(𝑀 + 𝐾))) | 
| 25 | 23, 2, 24 | syl2anr 597 | . . . . . . . . . . . . . . . . . 18
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → (𝑘 + 𝐾) ∈
(ℤ≥‘(𝑀 + 𝐾))) | 
| 26 | 21, 25 | eqeltrd 2840 | . . . . . . . . . . . . . . . . 17
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → (𝐾 + 𝑘) ∈ (ℤ≥‘(𝑀 + 𝐾))) | 
| 27 | 26, 4 | eleqtrrdi 2851 | . . . . . . . . . . . . . . . 16
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → (𝐾 + 𝑘) ∈ 𝑊) | 
| 28 |  | isumshft.3 | . . . . . . . . . . . . . . . . 17
⊢ (𝑗 = (𝐾 + 𝑘) → 𝐴 = 𝐵) | 
| 29 |  | eqid 2736 | . . . . . . . . . . . . . . . . 17
⊢ (𝑗 ∈ 𝑊 ↦ 𝐴) = (𝑗 ∈ 𝑊 ↦ 𝐴) | 
| 30 | 28, 29 | fvmpti 7014 | . . . . . . . . . . . . . . . 16
⊢ ((𝐾 + 𝑘) ∈ 𝑊 → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘)) = ( I ‘𝐵)) | 
| 31 | 27, 30 | syl 17 | . . . . . . . . . . . . . . 15
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘)) = ( I ‘𝐵)) | 
| 32 | 17, 31 | eqtr4d 2779 | . . . . . . . . . . . . . 14
⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘))) | 
| 33 | 32 | ralrimiva 3145 | . . . . . . . . . . . . 13
⊢ (𝜑 → ∀𝑘 ∈ 𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘))) | 
| 34 |  | nffvmpt1 6916 | . . . . . . . . . . . . . . 15
⊢
Ⅎ𝑘((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) | 
| 35 | 34 | nfeq1 2920 | . . . . . . . . . . . . . 14
⊢
Ⅎ𝑘((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)) | 
| 36 |  | fveq2 6905 | . . . . . . . . . . . . . . 15
⊢ (𝑘 = 𝑛 → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛)) | 
| 37 |  | oveq2 7440 | . . . . . . . . . . . . . . . 16
⊢ (𝑘 = 𝑛 → (𝐾 + 𝑘) = (𝐾 + 𝑛)) | 
| 38 | 37 | fveq2d 6909 | . . . . . . . . . . . . . . 15
⊢ (𝑘 = 𝑛 → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘)) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛))) | 
| 39 | 36, 38 | eqeq12d 2752 | . . . . . . . . . . . . . 14
⊢ (𝑘 = 𝑛 → (((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘)) ↔ ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)))) | 
| 40 | 35, 39 | rspc 3609 | . . . . . . . . . . . . 13
⊢ (𝑛 ∈ 𝑍 → (∀𝑘 ∈ 𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑘) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑘)) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)))) | 
| 41 | 33, 40 | mpan9 506 | . . . . . . . . . . . 12
⊢ ((𝜑 ∧ 𝑛 ∈ 𝑍) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛))) | 
| 42 | 41 | ralrimiva 3145 | . . . . . . . . . . 11
⊢ (𝜑 → ∀𝑛 ∈ 𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛))) | 
| 43 | 1 | adantr 480 | . . . . . . . . . . . . 13
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → 𝑀 ∈ ℤ) | 
| 44 | 2 | adantr 480 | . . . . . . . . . . . . 13
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → 𝐾 ∈ ℤ) | 
| 45 |  | simpr 484 | . . . . . . . . . . . . . 14
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → 𝑚 ∈ 𝑊) | 
| 46 | 45, 4 | eleqtrdi 2850 | . . . . . . . . . . . . 13
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → 𝑚 ∈ (ℤ≥‘(𝑀 + 𝐾))) | 
| 47 |  | eluzsub 12909 | . . . . . . . . . . . . 13
⊢ ((𝑀 ∈ ℤ ∧ 𝐾 ∈ ℤ ∧ 𝑚 ∈
(ℤ≥‘(𝑀 + 𝐾))) → (𝑚 − 𝐾) ∈ (ℤ≥‘𝑀)) | 
| 48 | 43, 44, 46, 47 | syl3anc 1372 | . . . . . . . . . . . 12
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → (𝑚 − 𝐾) ∈ (ℤ≥‘𝑀)) | 
| 49 | 48, 9 | eleqtrrdi 2851 | . . . . . . . . . . 11
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → (𝑚 − 𝐾) ∈ 𝑍) | 
| 50 |  | fveq2 6905 | . . . . . . . . . . . . 13
⊢ (𝑛 = (𝑚 − 𝐾) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑘 ∈ 𝑍 ↦ 𝐵)‘(𝑚 − 𝐾))) | 
| 51 |  | oveq2 7440 | . . . . . . . . . . . . . 14
⊢ (𝑛 = (𝑚 − 𝐾) → (𝐾 + 𝑛) = (𝐾 + (𝑚 − 𝐾))) | 
| 52 | 51 | fveq2d 6909 | . . . . . . . . . . . . 13
⊢ (𝑛 = (𝑚 − 𝐾) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + (𝑚 − 𝐾)))) | 
| 53 | 50, 52 | eqeq12d 2752 | . . . . . . . . . . . 12
⊢ (𝑛 = (𝑚 − 𝐾) → (((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)) ↔ ((𝑘 ∈ 𝑍 ↦ 𝐵)‘(𝑚 − 𝐾)) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + (𝑚 − 𝐾))))) | 
| 54 | 53 | rspccva 3620 | . . . . . . . . . . 11
⊢
((∀𝑛 ∈
𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)) ∧ (𝑚 − 𝐾) ∈ 𝑍) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘(𝑚 − 𝐾)) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + (𝑚 − 𝐾)))) | 
| 55 | 42, 49, 54 | syl2an2r 685 | . . . . . . . . . 10
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘(𝑚 − 𝐾)) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + (𝑚 − 𝐾)))) | 
| 56 |  | pncan3 11517 | . . . . . . . . . . . 12
⊢ ((𝐾 ∈ ℂ ∧ 𝑚 ∈ ℂ) → (𝐾 + (𝑚 − 𝐾)) = 𝑚) | 
| 57 | 6, 8, 56 | syl2an 596 | . . . . . . . . . . 11
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → (𝐾 + (𝑚 − 𝐾)) = 𝑚) | 
| 58 | 57 | fveq2d 6909 | . . . . . . . . . 10
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + (𝑚 − 𝐾))) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚)) | 
| 59 | 13, 55, 58 | 3eqtrrd 2781 | . . . . . . . . 9
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) = (((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)‘𝑚)) | 
| 60 | 5, 59 | sylan2br 595 | . . . . . . . 8
⊢ ((𝜑 ∧ 𝑚 ∈ (ℤ≥‘(𝑀 + 𝐾))) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) = (((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)‘𝑚)) | 
| 61 | 3, 60 | seqfeq 14069 | . . . . . . 7
⊢ (𝜑 → seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴)) = seq(𝑀 + 𝐾)( + , ((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾))) | 
| 62 | 61 | breq1d 5152 | . . . . . 6
⊢ (𝜑 → (seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴)) ⇝ 𝑥 ↔ seq(𝑀 + 𝐾)( + , ((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)) ⇝ 𝑥)) | 
| 63 | 11 | isershft 15701 | . . . . . . 7
⊢ ((𝑀 ∈ ℤ ∧ 𝐾 ∈ ℤ) →
(seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)) ⇝ 𝑥 ↔ seq(𝑀 + 𝐾)( + , ((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)) ⇝ 𝑥)) | 
| 64 | 1, 2, 63 | syl2anc 584 | . . . . . 6
⊢ (𝜑 → (seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)) ⇝ 𝑥 ↔ seq(𝑀 + 𝐾)( + , ((𝑘 ∈ 𝑍 ↦ 𝐵) shift 𝐾)) ⇝ 𝑥)) | 
| 65 | 62, 64 | bitr4d 282 | . . . . 5
⊢ (𝜑 → (seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴)) ⇝ 𝑥 ↔ seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)) ⇝ 𝑥)) | 
| 66 | 65 | iotabidv 6544 | . . . 4
⊢ (𝜑 → (℩𝑥seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴)) ⇝ 𝑥) = (℩𝑥seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)) ⇝ 𝑥)) | 
| 67 |  | df-fv 6568 | . . . 4
⊢ ( ⇝
‘seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴))) = (℩𝑥seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴)) ⇝ 𝑥) | 
| 68 |  | df-fv 6568 | . . . 4
⊢ ( ⇝
‘seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵))) = (℩𝑥seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)) ⇝ 𝑥) | 
| 69 | 66, 67, 68 | 3eqtr4g 2801 | . . 3
⊢ (𝜑 → ( ⇝ ‘seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴))) = ( ⇝ ‘seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)))) | 
| 70 |  | eqidd 2737 | . . . 4
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) = ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚)) | 
| 71 |  | isumshft.6 | . . . . . 6
⊢ ((𝜑 ∧ 𝑗 ∈ 𝑊) → 𝐴 ∈ ℂ) | 
| 72 | 71 | fmpttd 7134 | . . . . 5
⊢ (𝜑 → (𝑗 ∈ 𝑊 ↦ 𝐴):𝑊⟶ℂ) | 
| 73 | 72 | ffvelcdmda 7103 | . . . 4
⊢ ((𝜑 ∧ 𝑚 ∈ 𝑊) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) ∈ ℂ) | 
| 74 | 4, 3, 70, 73 | isum 15756 | . . 3
⊢ (𝜑 → Σ𝑚 ∈ 𝑊 ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) = ( ⇝ ‘seq(𝑀 + 𝐾)( + , (𝑗 ∈ 𝑊 ↦ 𝐴)))) | 
| 75 |  | eqidd 2737 | . . . 4
⊢ ((𝜑 ∧ 𝑛 ∈ 𝑍) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛)) | 
| 76 | 27 | ralrimiva 3145 | . . . . . . 7
⊢ (𝜑 → ∀𝑘 ∈ 𝑍 (𝐾 + 𝑘) ∈ 𝑊) | 
| 77 | 37 | eleq1d 2825 | . . . . . . . 8
⊢ (𝑘 = 𝑛 → ((𝐾 + 𝑘) ∈ 𝑊 ↔ (𝐾 + 𝑛) ∈ 𝑊)) | 
| 78 | 77 | rspccva 3620 | . . . . . . 7
⊢
((∀𝑘 ∈
𝑍 (𝐾 + 𝑘) ∈ 𝑊 ∧ 𝑛 ∈ 𝑍) → (𝐾 + 𝑛) ∈ 𝑊) | 
| 79 | 76, 78 | sylan 580 | . . . . . 6
⊢ ((𝜑 ∧ 𝑛 ∈ 𝑍) → (𝐾 + 𝑛) ∈ 𝑊) | 
| 80 |  | ffvelcdm 7100 | . . . . . 6
⊢ (((𝑗 ∈ 𝑊 ↦ 𝐴):𝑊⟶ℂ ∧ (𝐾 + 𝑛) ∈ 𝑊) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)) ∈ ℂ) | 
| 81 | 72, 79, 80 | syl2an2r 685 | . . . . 5
⊢ ((𝜑 ∧ 𝑛 ∈ 𝑍) → ((𝑗 ∈ 𝑊 ↦ 𝐴)‘(𝐾 + 𝑛)) ∈ ℂ) | 
| 82 | 41, 81 | eqeltrd 2840 | . . . 4
⊢ ((𝜑 ∧ 𝑛 ∈ 𝑍) → ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) ∈ ℂ) | 
| 83 | 9, 1, 75, 82 | isum 15756 | . . 3
⊢ (𝜑 → Σ𝑛 ∈ 𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = ( ⇝ ‘seq𝑀( + , (𝑘 ∈ 𝑍 ↦ 𝐵)))) | 
| 84 | 69, 74, 83 | 3eqtr4d 2786 | . 2
⊢ (𝜑 → Σ𝑚 ∈ 𝑊 ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) = Σ𝑛 ∈ 𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛)) | 
| 85 |  | sumfc 15746 | . 2
⊢
Σ𝑚 ∈
𝑊 ((𝑗 ∈ 𝑊 ↦ 𝐴)‘𝑚) = Σ𝑗 ∈ 𝑊 𝐴 | 
| 86 |  | sumfc 15746 | . 2
⊢
Σ𝑛 ∈
𝑍 ((𝑘 ∈ 𝑍 ↦ 𝐵)‘𝑛) = Σ𝑘 ∈ 𝑍 𝐵 | 
| 87 | 84, 85, 86 | 3eqtr3g 2799 | 1
⊢ (𝜑 → Σ𝑗 ∈ 𝑊 𝐴 = Σ𝑘 ∈ 𝑍 𝐵) |