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Mirrors > Home > MPE Home > Th. List > Mathboxes > frege53b | Structured version Visualization version GIF version |
Description: Lemma for frege102 (via frege92 42315). Proposition 53 of [Frege1879] p. 50. (Contributed by RP, 24-Dec-2019.) (Proof modification is discouraged.) |
Ref | Expression |
---|---|
frege53b | ⊢ ([𝑦 / 𝑥]𝜑 → (𝑦 = 𝑧 → [𝑧 / 𝑥]𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frege52b 42249 | . 2 ⊢ (𝑦 = 𝑧 → ([𝑦 / 𝑥]𝜑 → [𝑧 / 𝑥]𝜑)) | |
2 | ax-frege8 42169 | . 2 ⊢ ((𝑦 = 𝑧 → ([𝑦 / 𝑥]𝜑 → [𝑧 / 𝑥]𝜑)) → ([𝑦 / 𝑥]𝜑 → (𝑦 = 𝑧 → [𝑧 / 𝑥]𝜑))) | |
3 | 1, 2 | ax-mp 5 | 1 ⊢ ([𝑦 / 𝑥]𝜑 → (𝑦 = 𝑧 → [𝑧 / 𝑥]𝜑)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 [wsb 2068 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1914 ax-6 1972 ax-7 2012 ax-8 2109 ax-9 2117 ax-ext 2704 ax-frege8 42169 ax-frege52c 42248 |
This theorem depends on definitions: df-bi 206 df-an 398 df-ex 1783 df-clab 2711 df-cleq 2725 df-clel 2811 df-sbc 3741 |
This theorem is referenced by: frege55lem2b 42256 |
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