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Mirrors > Home > MPE Home > Th. List > euequ | Structured version Visualization version GIF version |
Description: There exists a unique set equal to a given set. Special case of eueqi 3702 proved using only predicate calculus. The proof needs 𝑦 = 𝑧 be free of 𝑥. This is ensured by having 𝑥 and 𝑦 be distinct. Alternately, a distinctor ¬ ∀𝑥𝑥 = 𝑦 could have been used instead. See eueq 3701 and eueqi 3702 for classes. (Contributed by Stefan Allan, 4-Dec-2008.) (Proof shortened by Wolf Lammen, 8-Sep-2019.) Reduce axiom usage. (Revised by Wolf Lammen, 1-Mar-2023.) |
Ref | Expression |
---|---|
euequ | ⊢ ∃!𝑥 𝑥 = 𝑦 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax6ev 1972 | . 2 ⊢ ∃𝑥 𝑥 = 𝑦 | |
2 | ax6ev 1972 | . . 3 ⊢ ∃𝑧 𝑧 = 𝑦 | |
3 | equeuclr 2030 | . . . 4 ⊢ (𝑧 = 𝑦 → (𝑥 = 𝑦 → 𝑥 = 𝑧)) | |
4 | 3 | alrimiv 1928 | . . 3 ⊢ (𝑧 = 𝑦 → ∀𝑥(𝑥 = 𝑦 → 𝑥 = 𝑧)) |
5 | 2, 4 | eximii 1837 | . 2 ⊢ ∃𝑧∀𝑥(𝑥 = 𝑦 → 𝑥 = 𝑧) |
6 | eu3v 2655 | . 2 ⊢ (∃!𝑥 𝑥 = 𝑦 ↔ (∃𝑥 𝑥 = 𝑦 ∧ ∃𝑧∀𝑥(𝑥 = 𝑦 → 𝑥 = 𝑧))) | |
7 | 1, 5, 6 | mpbir2an 709 | 1 ⊢ ∃!𝑥 𝑥 = 𝑦 |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∀wal 1535 ∃wex 1780 ∃!weu 2653 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 |
This theorem depends on definitions: df-bi 209 df-an 399 df-ex 1781 df-mo 2622 df-eu 2654 |
This theorem is referenced by: axsepgfromrep 5203 copsexgw 5383 copsexg 5384 oprabidw 7189 oprabid 7190 |
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