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Mirrors > Home > MPE Home > Th. List > df-en | Structured version Visualization version GIF version |
Description: Define the equinumerosity relation. Definition of [Enderton] p. 129. We define ≈ to be a binary relation rather than a connective, so its arguments must be sets to be meaningful. This is acceptable because we do not consider equinumerosity for proper classes. We derive the usual definition as bren 7964. (Contributed by NM, 28-Mar-1998.) |
Ref | Expression |
---|---|
df-en | ⊢ ≈ = {〈𝑥, 𝑦〉 ∣ ∃𝑓 𝑓:𝑥–1-1-onto→𝑦} |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cen 7952 | . 2 class ≈ | |
2 | vx | . . . . . 6 setvar 𝑥 | |
3 | 2 | cv 1482 | . . . . 5 class 𝑥 |
4 | vy | . . . . . 6 setvar 𝑦 | |
5 | 4 | cv 1482 | . . . . 5 class 𝑦 |
6 | vf | . . . . . 6 setvar 𝑓 | |
7 | 6 | cv 1482 | . . . . 5 class 𝑓 |
8 | 3, 5, 7 | wf1o 5887 | . . . 4 wff 𝑓:𝑥–1-1-onto→𝑦 |
9 | 8, 6 | wex 1704 | . . 3 wff ∃𝑓 𝑓:𝑥–1-1-onto→𝑦 |
10 | 9, 2, 4 | copab 4712 | . 2 class {〈𝑥, 𝑦〉 ∣ ∃𝑓 𝑓:𝑥–1-1-onto→𝑦} |
11 | 1, 10 | wceq 1483 | 1 wff ≈ = {〈𝑥, 𝑦〉 ∣ ∃𝑓 𝑓:𝑥–1-1-onto→𝑦} |
Colors of variables: wff setvar class |
This definition is referenced by: relen 7960 bren 7964 enssdom 7980 |
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