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Mirrors > Home > ILE Home > Th. List > dtruarb | GIF version |
Description: At least two sets exist (or in terms of first-order logic, the universe of discourse has two or more objects). This theorem asserts the existence of two sets which do not equal each other; compare with dtruex 4560 in which we are given a set 𝑦 and go from there to a set 𝑥 which is not equal to it. (Contributed by Jim Kingdon, 2-Sep-2018.) |
Ref | Expression |
---|---|
dtruarb | ⊢ ∃𝑥∃𝑦 ¬ 𝑥 = 𝑦 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | el 4180 | . . 3 ⊢ ∃𝑥 𝑧 ∈ 𝑥 | |
2 | ax-nul 4131 | . . . 4 ⊢ ∃𝑦∀𝑧 ¬ 𝑧 ∈ 𝑦 | |
3 | sp 1511 | . . . 4 ⊢ (∀𝑧 ¬ 𝑧 ∈ 𝑦 → ¬ 𝑧 ∈ 𝑦) | |
4 | 2, 3 | eximii 1602 | . . 3 ⊢ ∃𝑦 ¬ 𝑧 ∈ 𝑦 |
5 | eeanv 1932 | . . 3 ⊢ (∃𝑥∃𝑦(𝑧 ∈ 𝑥 ∧ ¬ 𝑧 ∈ 𝑦) ↔ (∃𝑥 𝑧 ∈ 𝑥 ∧ ∃𝑦 ¬ 𝑧 ∈ 𝑦)) | |
6 | 1, 4, 5 | mpbir2an 942 | . 2 ⊢ ∃𝑥∃𝑦(𝑧 ∈ 𝑥 ∧ ¬ 𝑧 ∈ 𝑦) |
7 | nelneq2 2279 | . . 3 ⊢ ((𝑧 ∈ 𝑥 ∧ ¬ 𝑧 ∈ 𝑦) → ¬ 𝑥 = 𝑦) | |
8 | 7 | 2eximi 1601 | . 2 ⊢ (∃𝑥∃𝑦(𝑧 ∈ 𝑥 ∧ ¬ 𝑧 ∈ 𝑦) → ∃𝑥∃𝑦 ¬ 𝑥 = 𝑦) |
9 | 6, 8 | ax-mp 5 | 1 ⊢ ∃𝑥∃𝑦 ¬ 𝑥 = 𝑦 |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 ∧ wa 104 ∀wal 1351 ∃wex 1492 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-in1 614 ax-in2 615 ax-5 1447 ax-7 1448 ax-gen 1449 ax-ie1 1493 ax-ie2 1494 ax-8 1504 ax-4 1510 ax-17 1526 ax-i9 1530 ax-ial 1534 ax-13 2150 ax-14 2151 ax-ext 2159 ax-nul 4131 ax-pow 4176 |
This theorem depends on definitions: df-bi 117 df-nf 1461 df-cleq 2170 df-clel 2173 |
This theorem is referenced by: (None) |
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