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Mirrors > Home > MPE Home > Th. List > equsexALT | Structured version Visualization version GIF version |
Description: Alternate proof of equsex 2281. This proves the result directly, instead of as a corollary of equsal 2279 via equs4 2278. Note in particular that only existential quantifiers appear in the proof and that the only step requiring ax-13 2234 is ax6e 2238. This proof mimics that of equsal 2279 (in particular, note pm5.32i 667, exbii 1764, 19.41 2090, mpbiran 955 correspond respectively to pm5.74i 259, albii 1737, 19.23 2067, a1bi 351). (Contributed by BJ, 20-Aug-2020.) (Proof modification is discouraged.) (New usage is discouraged.) |
Ref | Expression |
---|---|
equsex.nf | ⊢ Ⅎ𝑥𝜓 |
equsex.1 | ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) |
Ref | Expression |
---|---|
equsexALT | ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) ↔ 𝜓) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | equsex.1 | . . . 4 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) | |
2 | 1 | pm5.32i 667 | . . 3 ⊢ ((𝑥 = 𝑦 ∧ 𝜑) ↔ (𝑥 = 𝑦 ∧ 𝜓)) |
3 | 2 | exbii 1764 | . 2 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) ↔ ∃𝑥(𝑥 = 𝑦 ∧ 𝜓)) |
4 | ax6e 2238 | . . 3 ⊢ ∃𝑥 𝑥 = 𝑦 | |
5 | equsex.nf | . . . 4 ⊢ Ⅎ𝑥𝜓 | |
6 | 5 | 19.41 2090 | . . 3 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜓) ↔ (∃𝑥 𝑥 = 𝑦 ∧ 𝜓)) |
7 | 4, 6 | mpbiran 955 | . 2 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜓) ↔ 𝜓) |
8 | 3, 7 | bitri 263 | 1 ⊢ (∃𝑥(𝑥 = 𝑦 ∧ 𝜑) ↔ 𝜓) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 195 ∧ wa 383 ∃wex 1695 Ⅎwnf 1699 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-12 2034 ax-13 2234 |
This theorem depends on definitions: df-bi 196 df-an 385 df-ex 1696 df-nf 1701 |
This theorem is referenced by: (None) |
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