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Mirrors > Home > ILE Home > Th. List > sbco2d | GIF version |
Description: A composition law for substitution. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
sbco2d.1 | ⊢ (𝜑 → ∀𝑥𝜑) |
sbco2d.2 | ⊢ (𝜑 → ∀𝑧𝜑) |
sbco2d.3 | ⊢ (𝜑 → (𝜓 → ∀𝑧𝜓)) |
Ref | Expression |
---|---|
sbco2d | ⊢ (𝜑 → ([𝑦 / 𝑧][𝑧 / 𝑥]𝜓 ↔ [𝑦 / 𝑥]𝜓)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sbco2d.2 | . . . . 5 ⊢ (𝜑 → ∀𝑧𝜑) | |
2 | sbco2d.3 | . . . . 5 ⊢ (𝜑 → (𝜓 → ∀𝑧𝜓)) | |
3 | 1, 2 | hbim1 1502 | . . . 4 ⊢ ((𝜑 → 𝜓) → ∀𝑧(𝜑 → 𝜓)) |
4 | 3 | sbco2h 1879 | . . 3 ⊢ ([𝑦 / 𝑧][𝑧 / 𝑥](𝜑 → 𝜓) ↔ [𝑦 / 𝑥](𝜑 → 𝜓)) |
5 | sbco2d.1 | . . . . . 6 ⊢ (𝜑 → ∀𝑥𝜑) | |
6 | 5 | sbrim 1871 | . . . . 5 ⊢ ([𝑧 / 𝑥](𝜑 → 𝜓) ↔ (𝜑 → [𝑧 / 𝑥]𝜓)) |
7 | 6 | sbbii 1688 | . . . 4 ⊢ ([𝑦 / 𝑧][𝑧 / 𝑥](𝜑 → 𝜓) ↔ [𝑦 / 𝑧](𝜑 → [𝑧 / 𝑥]𝜓)) |
8 | 1 | sbrim 1871 | . . . 4 ⊢ ([𝑦 / 𝑧](𝜑 → [𝑧 / 𝑥]𝜓) ↔ (𝜑 → [𝑦 / 𝑧][𝑧 / 𝑥]𝜓)) |
9 | 7, 8 | bitri 182 | . . 3 ⊢ ([𝑦 / 𝑧][𝑧 / 𝑥](𝜑 → 𝜓) ↔ (𝜑 → [𝑦 / 𝑧][𝑧 / 𝑥]𝜓)) |
10 | 5 | sbrim 1871 | . . 3 ⊢ ([𝑦 / 𝑥](𝜑 → 𝜓) ↔ (𝜑 → [𝑦 / 𝑥]𝜓)) |
11 | 4, 9, 10 | 3bitr3i 208 | . 2 ⊢ ((𝜑 → [𝑦 / 𝑧][𝑧 / 𝑥]𝜓) ↔ (𝜑 → [𝑦 / 𝑥]𝜓)) |
12 | 11 | pm5.74ri 179 | 1 ⊢ (𝜑 → ([𝑦 / 𝑧][𝑧 / 𝑥]𝜓 ↔ [𝑦 / 𝑥]𝜓)) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ↔ wb 103 ∀wal 1282 [wsb 1685 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-io 662 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-10 1436 ax-11 1437 ax-i12 1438 ax-bndl 1439 ax-4 1440 ax-17 1459 ax-i9 1463 ax-ial 1467 ax-i5r 1468 |
This theorem depends on definitions: df-bi 115 df-nf 1390 df-sb 1686 |
This theorem is referenced by: (None) |
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