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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | ixpsnf1o 8501* | A bijection between a class and single-point functions to it. (Contributed by Stefan O'Rear, 24-Jan-2015.) |
⊢ 𝐹 = (𝑥 ∈ 𝐴 ↦ ({𝐼} × {𝑥})) ⇒ ⊢ (𝐼 ∈ 𝑉 → 𝐹:𝐴–1-1-onto→X𝑦 ∈ {𝐼}𝐴) | ||
Theorem | mapsnf1o 8502* | A bijection between a set and single-point functions to it. (Contributed by Stefan O'Rear, 24-Jan-2015.) |
⊢ 𝐹 = (𝑥 ∈ 𝐴 ↦ ({𝐼} × {𝑥})) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐼 ∈ 𝑊) → 𝐹:𝐴–1-1-onto→(𝐴 ↑m {𝐼})) | ||
Theorem | boxriin 8503* | A rectangular subset of a rectangular set can be recovered as the relative intersection of single-axis restrictions. (Contributed by Stefan O'Rear, 22-Feb-2015.) |
⊢ (∀𝑥 ∈ 𝐼 𝐴 ⊆ 𝐵 → X𝑥 ∈ 𝐼 𝐴 = (X𝑥 ∈ 𝐼 𝐵 ∩ ∩ 𝑦 ∈ 𝐼 X𝑥 ∈ 𝐼 if(𝑥 = 𝑦, 𝐴, 𝐵))) | ||
Theorem | boxcutc 8504* | The relative complement of a box set restricted on one axis. (Contributed by Stefan O'Rear, 22-Feb-2015.) |
⊢ ((𝑋 ∈ 𝐴 ∧ ∀𝑘 ∈ 𝐴 𝐶 ⊆ 𝐵) → (X𝑘 ∈ 𝐴 𝐵 ∖ X𝑘 ∈ 𝐴 if(𝑘 = 𝑋, 𝐶, 𝐵)) = X𝑘 ∈ 𝐴 if(𝑘 = 𝑋, (𝐵 ∖ 𝐶), 𝐵)) | ||
Syntax | cen 8505 | Extend class definition to include the equinumerosity relation ("approximately equals" symbol) |
class ≈ | ||
Syntax | cdom 8506 | Extend class definition to include the dominance relation (curly "less than or equal to") |
class ≼ | ||
Syntax | csdm 8507 | Extend class definition to include the strict dominance relation (curly less-than) |
class ≺ | ||
Syntax | cfn 8508 | Extend class definition to include the class of all finite sets. |
class Fin | ||
Definition | df-en 8509* | 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 8517. (Contributed by NM, 28-Mar-1998.) |
⊢ ≈ = {〈𝑥, 𝑦〉 ∣ ∃𝑓 𝑓:𝑥–1-1-onto→𝑦} | ||
Definition | df-dom 8510* | Define the dominance relation. For an alternate definition see dfdom2 8534. Compare Definition of [Enderton] p. 145. Typical textbook definitions are derived as brdom 8520 and domen 8521. (Contributed by NM, 28-Mar-1998.) |
⊢ ≼ = {〈𝑥, 𝑦〉 ∣ ∃𝑓 𝑓:𝑥–1-1→𝑦} | ||
Definition | df-sdom 8511 | Define the strict dominance relation. Alternate possible definitions are derived as brsdom 8531 and brsdom2 8640. Definition 3 of [Suppes] p. 97. (Contributed by NM, 31-Mar-1998.) |
⊢ ≺ = ( ≼ ∖ ≈ ) | ||
Definition | df-fin 8512* | Define the (proper) class of all finite sets. Similar to Definition 10.29 of [TakeutiZaring] p. 91, whose "Fin(a)" corresponds to our "𝑎 ∈ Fin". This definition is meaningful whether or not we accept the Axiom of Infinity ax-inf2 9103. If we accept Infinity, we can also express 𝐴 ∈ Fin by 𝐴 ≺ ω (theorem isfinite 9114.) (Contributed by NM, 22-Aug-2008.) |
⊢ Fin = {𝑥 ∣ ∃𝑦 ∈ ω 𝑥 ≈ 𝑦} | ||
Theorem | relen 8513 | Equinumerosity is a relation. (Contributed by NM, 28-Mar-1998.) |
⊢ Rel ≈ | ||
Theorem | reldom 8514 | Dominance is a relation. (Contributed by NM, 28-Mar-1998.) |
⊢ Rel ≼ | ||
Theorem | relsdom 8515 | Strict dominance is a relation. (Contributed by NM, 31-Mar-1998.) |
⊢ Rel ≺ | ||
Theorem | encv 8516 | If two classes are equinumerous, both classes are sets. (Contributed by AV, 21-Mar-2019.) |
⊢ (𝐴 ≈ 𝐵 → (𝐴 ∈ V ∧ 𝐵 ∈ V)) | ||
Theorem | bren 8517* | Equinumerosity relation. (Contributed by NM, 15-Jun-1998.) |
⊢ (𝐴 ≈ 𝐵 ↔ ∃𝑓 𝑓:𝐴–1-1-onto→𝐵) | ||
Theorem | brdomg 8518* | Dominance relation. (Contributed by NM, 15-Jun-1998.) |
⊢ (𝐵 ∈ 𝐶 → (𝐴 ≼ 𝐵 ↔ ∃𝑓 𝑓:𝐴–1-1→𝐵)) | ||
Theorem | brdomi 8519* | Dominance relation. (Contributed by Mario Carneiro, 26-Apr-2015.) |
⊢ (𝐴 ≼ 𝐵 → ∃𝑓 𝑓:𝐴–1-1→𝐵) | ||
Theorem | brdom 8520* | Dominance relation. (Contributed by NM, 15-Jun-1998.) |
⊢ 𝐵 ∈ V ⇒ ⊢ (𝐴 ≼ 𝐵 ↔ ∃𝑓 𝑓:𝐴–1-1→𝐵) | ||
Theorem | domen 8521* | Dominance in terms of equinumerosity. Example 1 of [Enderton] p. 146. (Contributed by NM, 15-Jun-1998.) |
⊢ 𝐵 ∈ V ⇒ ⊢ (𝐴 ≼ 𝐵 ↔ ∃𝑥(𝐴 ≈ 𝑥 ∧ 𝑥 ⊆ 𝐵)) | ||
Theorem | domeng 8522* | Dominance in terms of equinumerosity, with the sethood requirement expressed as an antecedent. Example 1 of [Enderton] p. 146. (Contributed by NM, 24-Apr-2004.) |
⊢ (𝐵 ∈ 𝐶 → (𝐴 ≼ 𝐵 ↔ ∃𝑥(𝐴 ≈ 𝑥 ∧ 𝑥 ⊆ 𝐵))) | ||
Theorem | ctex 8523 | A countable set is a set. (Contributed by Thierry Arnoux, 29-Dec-2016.) (Proof shortened by Jim Kingdon, 13-Mar-2023.) |
⊢ (𝐴 ≼ ω → 𝐴 ∈ V) | ||
Theorem | f1oen3g 8524 | The domain and range of a one-to-one, onto function are equinumerous. This variation of f1oeng 8527 does not require the Axiom of Replacement. (Contributed by NM, 13-Jan-2007.) (Revised by Mario Carneiro, 10-Sep-2015.) |
⊢ ((𝐹 ∈ 𝑉 ∧ 𝐹:𝐴–1-1-onto→𝐵) → 𝐴 ≈ 𝐵) | ||
Theorem | f1oen2g 8525 | The domain and range of a one-to-one, onto function are equinumerous. This variation of f1oeng 8527 does not require the Axiom of Replacement. (Contributed by Mario Carneiro, 10-Sep-2015.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐹:𝐴–1-1-onto→𝐵) → 𝐴 ≈ 𝐵) | ||
Theorem | f1dom2g 8526 | The domain of a one-to-one function is dominated by its codomain. This variation of f1domg 8528 does not require the Axiom of Replacement. (Contributed by Mario Carneiro, 24-Jun-2015.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐹:𝐴–1-1→𝐵) → 𝐴 ≼ 𝐵) | ||
Theorem | f1oeng 8527 | The domain and range of a one-to-one, onto function are equinumerous. (Contributed by NM, 19-Jun-1998.) |
⊢ ((𝐴 ∈ 𝐶 ∧ 𝐹:𝐴–1-1-onto→𝐵) → 𝐴 ≈ 𝐵) | ||
Theorem | f1domg 8528 | The domain of a one-to-one function is dominated by its codomain. (Contributed by NM, 4-Sep-2004.) |
⊢ (𝐵 ∈ 𝐶 → (𝐹:𝐴–1-1→𝐵 → 𝐴 ≼ 𝐵)) | ||
Theorem | f1oen 8529 | The domain and range of a one-to-one, onto function are equinumerous. (Contributed by NM, 19-Jun-1998.) |
⊢ 𝐴 ∈ V ⇒ ⊢ (𝐹:𝐴–1-1-onto→𝐵 → 𝐴 ≈ 𝐵) | ||
Theorem | f1dom 8530 | The domain of a one-to-one function is dominated by its codomain. (Contributed by NM, 19-Jun-1998.) |
⊢ 𝐵 ∈ V ⇒ ⊢ (𝐹:𝐴–1-1→𝐵 → 𝐴 ≼ 𝐵) | ||
Theorem | brsdom 8531 | Strict dominance relation, meaning "𝐵 is strictly greater in size than 𝐴". Definition of [Mendelson] p. 255. (Contributed by NM, 25-Jun-1998.) |
⊢ (𝐴 ≺ 𝐵 ↔ (𝐴 ≼ 𝐵 ∧ ¬ 𝐴 ≈ 𝐵)) | ||
Theorem | isfi 8532* | Express "𝐴 is finite." Definition 10.29 of [TakeutiZaring] p. 91 (whose "Fin " is a predicate instead of a class). (Contributed by NM, 22-Aug-2008.) |
⊢ (𝐴 ∈ Fin ↔ ∃𝑥 ∈ ω 𝐴 ≈ 𝑥) | ||
Theorem | enssdom 8533 | Equinumerosity implies dominance. (Contributed by NM, 31-Mar-1998.) |
⊢ ≈ ⊆ ≼ | ||
Theorem | dfdom2 8534 | Alternate definition of dominance. (Contributed by NM, 17-Jun-1998.) |
⊢ ≼ = ( ≺ ∪ ≈ ) | ||
Theorem | endom 8535 | Equinumerosity implies dominance. Theorem 15 of [Suppes] p. 94. (Contributed by NM, 28-May-1998.) |
⊢ (𝐴 ≈ 𝐵 → 𝐴 ≼ 𝐵) | ||
Theorem | sdomdom 8536 | Strict dominance implies dominance. (Contributed by NM, 10-Jun-1998.) |
⊢ (𝐴 ≺ 𝐵 → 𝐴 ≼ 𝐵) | ||
Theorem | sdomnen 8537 | Strict dominance implies non-equinumerosity. (Contributed by NM, 10-Jun-1998.) |
⊢ (𝐴 ≺ 𝐵 → ¬ 𝐴 ≈ 𝐵) | ||
Theorem | brdom2 8538 | Dominance in terms of strict dominance and equinumerosity. Theorem 22(iv) of [Suppes] p. 97. (Contributed by NM, 17-Jun-1998.) |
⊢ (𝐴 ≼ 𝐵 ↔ (𝐴 ≺ 𝐵 ∨ 𝐴 ≈ 𝐵)) | ||
Theorem | bren2 8539 | Equinumerosity expressed in terms of dominance and strict dominance. (Contributed by NM, 23-Oct-2004.) |
⊢ (𝐴 ≈ 𝐵 ↔ (𝐴 ≼ 𝐵 ∧ ¬ 𝐴 ≺ 𝐵)) | ||
Theorem | enrefg 8540 | Equinumerosity is reflexive. Theorem 1 of [Suppes] p. 92. (Contributed by NM, 18-Jun-1998.) (Revised by Mario Carneiro, 26-Apr-2015.) |
⊢ (𝐴 ∈ 𝑉 → 𝐴 ≈ 𝐴) | ||
Theorem | enref 8541 | Equinumerosity is reflexive. Theorem 1 of [Suppes] p. 92. (Contributed by NM, 25-Sep-2004.) |
⊢ 𝐴 ∈ V ⇒ ⊢ 𝐴 ≈ 𝐴 | ||
Theorem | eqeng 8542 | Equality implies equinumerosity. (Contributed by NM, 26-Oct-2003.) |
⊢ (𝐴 ∈ 𝑉 → (𝐴 = 𝐵 → 𝐴 ≈ 𝐵)) | ||
Theorem | domrefg 8543 | Dominance is reflexive. (Contributed by NM, 18-Jun-1998.) |
⊢ (𝐴 ∈ 𝑉 → 𝐴 ≼ 𝐴) | ||
Theorem | en2d 8544* | Equinumerosity inference from an implicit one-to-one onto function. (Contributed by NM, 27-Jul-2004.) (Revised by Mario Carneiro, 12-May-2014.) |
⊢ (𝜑 → 𝐴 ∈ V) & ⊢ (𝜑 → 𝐵 ∈ V) & ⊢ (𝜑 → (𝑥 ∈ 𝐴 → 𝐶 ∈ V)) & ⊢ (𝜑 → (𝑦 ∈ 𝐵 → 𝐷 ∈ V)) & ⊢ (𝜑 → ((𝑥 ∈ 𝐴 ∧ 𝑦 = 𝐶) ↔ (𝑦 ∈ 𝐵 ∧ 𝑥 = 𝐷))) ⇒ ⊢ (𝜑 → 𝐴 ≈ 𝐵) | ||
Theorem | en3d 8545* | Equinumerosity inference from an implicit one-to-one onto function. (Contributed by NM, 27-Jul-2004.) (Revised by Mario Carneiro, 12-May-2014.) |
⊢ (𝜑 → 𝐴 ∈ V) & ⊢ (𝜑 → 𝐵 ∈ V) & ⊢ (𝜑 → (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵)) & ⊢ (𝜑 → (𝑦 ∈ 𝐵 → 𝐷 ∈ 𝐴)) & ⊢ (𝜑 → ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) → (𝑥 = 𝐷 ↔ 𝑦 = 𝐶))) ⇒ ⊢ (𝜑 → 𝐴 ≈ 𝐵) | ||
Theorem | en2i 8546* | Equinumerosity inference from an implicit one-to-one onto function. (Contributed by NM, 4-Jan-2004.) |
⊢ 𝐴 ∈ V & ⊢ 𝐵 ∈ V & ⊢ (𝑥 ∈ 𝐴 → 𝐶 ∈ V) & ⊢ (𝑦 ∈ 𝐵 → 𝐷 ∈ V) & ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑦 = 𝐶) ↔ (𝑦 ∈ 𝐵 ∧ 𝑥 = 𝐷)) ⇒ ⊢ 𝐴 ≈ 𝐵 | ||
Theorem | en3i 8547* | Equinumerosity inference from an implicit one-to-one onto function. (Contributed by NM, 19-Jul-2004.) |
⊢ 𝐴 ∈ V & ⊢ 𝐵 ∈ V & ⊢ (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵) & ⊢ (𝑦 ∈ 𝐵 → 𝐷 ∈ 𝐴) & ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) → (𝑥 = 𝐷 ↔ 𝑦 = 𝐶)) ⇒ ⊢ 𝐴 ≈ 𝐵 | ||
Theorem | dom2lem 8548* | A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its codomain. (Contributed by NM, 24-Jul-2004.) |
⊢ (𝜑 → (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵)) & ⊢ (𝜑 → ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐶 = 𝐷 ↔ 𝑥 = 𝑦))) ⇒ ⊢ (𝜑 → (𝑥 ∈ 𝐴 ↦ 𝐶):𝐴–1-1→𝐵) | ||
Theorem | dom2d 8549* | A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its codomain. (Contributed by NM, 24-Jul-2004.) (Revised by Mario Carneiro, 20-May-2013.) |
⊢ (𝜑 → (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵)) & ⊢ (𝜑 → ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐶 = 𝐷 ↔ 𝑥 = 𝑦))) ⇒ ⊢ (𝜑 → (𝐵 ∈ 𝑅 → 𝐴 ≼ 𝐵)) | ||
Theorem | dom3d 8550* | A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its codomain. (Contributed by Mario Carneiro, 20-May-2013.) |
⊢ (𝜑 → (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵)) & ⊢ (𝜑 → ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐶 = 𝐷 ↔ 𝑥 = 𝑦))) & ⊢ (𝜑 → 𝐴 ∈ 𝑉) & ⊢ (𝜑 → 𝐵 ∈ 𝑊) ⇒ ⊢ (𝜑 → 𝐴 ≼ 𝐵) | ||
Theorem | dom2 8551* | A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its codomain. 𝐶 and 𝐷 can be read 𝐶(𝑥) and 𝐷(𝑦), as can be inferred from their distinct variable conditions. (Contributed by NM, 26-Oct-2003.) |
⊢ (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵) & ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐶 = 𝐷 ↔ 𝑥 = 𝑦)) ⇒ ⊢ (𝐵 ∈ 𝑉 → 𝐴 ≼ 𝐵) | ||
Theorem | dom3 8552* | A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its codomain. 𝐶 and 𝐷 can be read 𝐶(𝑥) and 𝐷(𝑦), as can be inferred from their distinct variable conditions. (Contributed by Mario Carneiro, 20-May-2013.) |
⊢ (𝑥 ∈ 𝐴 → 𝐶 ∈ 𝐵) & ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐶 = 𝐷 ↔ 𝑥 = 𝑦)) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → 𝐴 ≼ 𝐵) | ||
Theorem | idssen 8553 | Equality implies equinumerosity. (Contributed by NM, 30-Apr-1998.) (Revised by Mario Carneiro, 15-Nov-2014.) |
⊢ I ⊆ ≈ | ||
Theorem | ssdomg 8554 | A set dominates its subsets. Theorem 16 of [Suppes] p. 94. (Contributed by NM, 19-Jun-1998.) (Revised by Mario Carneiro, 24-Jun-2015.) |
⊢ (𝐵 ∈ 𝑉 → (𝐴 ⊆ 𝐵 → 𝐴 ≼ 𝐵)) | ||
Theorem | ener 8555 | Equinumerosity is an equivalence relation. (Contributed by NM, 19-Mar-1998.) (Revised by Mario Carneiro, 15-Nov-2014.) (Proof shortened by AV, 1-May-2021.) |
⊢ ≈ Er V | ||
Theorem | ensymb 8556 | Symmetry of equinumerosity. Theorem 2 of [Suppes] p. 92. (Contributed by Mario Carneiro, 26-Apr-2015.) |
⊢ (𝐴 ≈ 𝐵 ↔ 𝐵 ≈ 𝐴) | ||
Theorem | ensym 8557 | Symmetry of equinumerosity. Theorem 2 of [Suppes] p. 92. (Contributed by NM, 26-Oct-2003.) (Revised by Mario Carneiro, 26-Apr-2015.) |
⊢ (𝐴 ≈ 𝐵 → 𝐵 ≈ 𝐴) | ||
Theorem | ensymi 8558 | Symmetry of equinumerosity. Theorem 2 of [Suppes] p. 92. (Contributed by NM, 25-Sep-2004.) |
⊢ 𝐴 ≈ 𝐵 ⇒ ⊢ 𝐵 ≈ 𝐴 | ||
Theorem | ensymd 8559 | Symmetry of equinumerosity. Deduction form of ensym 8557. (Contributed by David Moews, 1-May-2017.) |
⊢ (𝜑 → 𝐴 ≈ 𝐵) ⇒ ⊢ (𝜑 → 𝐵 ≈ 𝐴) | ||
Theorem | entr 8560 | Transitivity of equinumerosity. Theorem 3 of [Suppes] p. 92. (Contributed by NM, 9-Jun-1998.) |
⊢ ((𝐴 ≈ 𝐵 ∧ 𝐵 ≈ 𝐶) → 𝐴 ≈ 𝐶) | ||
Theorem | domtr 8561 | Transitivity of dominance relation. Theorem 17 of [Suppes] p. 94. (Contributed by NM, 4-Jun-1998.) (Revised by Mario Carneiro, 15-Nov-2014.) |
⊢ ((𝐴 ≼ 𝐵 ∧ 𝐵 ≼ 𝐶) → 𝐴 ≼ 𝐶) | ||
Theorem | entri 8562 | A chained equinumerosity inference. (Contributed by NM, 25-Sep-2004.) |
⊢ 𝐴 ≈ 𝐵 & ⊢ 𝐵 ≈ 𝐶 ⇒ ⊢ 𝐴 ≈ 𝐶 | ||
Theorem | entr2i 8563 | A chained equinumerosity inference. (Contributed by NM, 25-Sep-2004.) |
⊢ 𝐴 ≈ 𝐵 & ⊢ 𝐵 ≈ 𝐶 ⇒ ⊢ 𝐶 ≈ 𝐴 | ||
Theorem | entr3i 8564 | A chained equinumerosity inference. (Contributed by NM, 25-Sep-2004.) |
⊢ 𝐴 ≈ 𝐵 & ⊢ 𝐴 ≈ 𝐶 ⇒ ⊢ 𝐵 ≈ 𝐶 | ||
Theorem | entr4i 8565 | A chained equinumerosity inference. (Contributed by NM, 25-Sep-2004.) |
⊢ 𝐴 ≈ 𝐵 & ⊢ 𝐶 ≈ 𝐵 ⇒ ⊢ 𝐴 ≈ 𝐶 | ||
Theorem | endomtr 8566 | Transitivity of equinumerosity and dominance. (Contributed by NM, 7-Jun-1998.) |
⊢ ((𝐴 ≈ 𝐵 ∧ 𝐵 ≼ 𝐶) → 𝐴 ≼ 𝐶) | ||
Theorem | domentr 8567 | Transitivity of dominance and equinumerosity. (Contributed by NM, 7-Jun-1998.) |
⊢ ((𝐴 ≼ 𝐵 ∧ 𝐵 ≈ 𝐶) → 𝐴 ≼ 𝐶) | ||
Theorem | f1imaeng 8568 | A one-to-one function's image under a subset of its domain is equinumerous to the subset. (Contributed by Mario Carneiro, 15-May-2015.) |
⊢ ((𝐹:𝐴–1-1→𝐵 ∧ 𝐶 ⊆ 𝐴 ∧ 𝐶 ∈ 𝑉) → (𝐹 “ 𝐶) ≈ 𝐶) | ||
Theorem | f1imaen2g 8569 | A one-to-one function's image under a subset of its domain is equinumerous to the subset. (This version of f1imaen 8570 does not need ax-reg 9055.) (Contributed by Mario Carneiro, 16-Nov-2014.) (Revised by Mario Carneiro, 25-Jun-2015.) |
⊢ (((𝐹:𝐴–1-1→𝐵 ∧ 𝐵 ∈ 𝑉) ∧ (𝐶 ⊆ 𝐴 ∧ 𝐶 ∈ 𝑉)) → (𝐹 “ 𝐶) ≈ 𝐶) | ||
Theorem | f1imaen 8570 | A one-to-one function's image under a subset of its domain is equinumerous to the subset. (Contributed by NM, 30-Sep-2004.) |
⊢ 𝐶 ∈ V ⇒ ⊢ ((𝐹:𝐴–1-1→𝐵 ∧ 𝐶 ⊆ 𝐴) → (𝐹 “ 𝐶) ≈ 𝐶) | ||
Theorem | en0 8571 | The empty set is equinumerous only to itself. Exercise 1 of [TakeutiZaring] p. 88. (Contributed by NM, 27-May-1998.) |
⊢ (𝐴 ≈ ∅ ↔ 𝐴 = ∅) | ||
Theorem | ensn1 8572 | A singleton is equinumerous to ordinal one. (Contributed by NM, 4-Nov-2002.) |
⊢ 𝐴 ∈ V ⇒ ⊢ {𝐴} ≈ 1o | ||
Theorem | ensn1g 8573 | A singleton is equinumerous to ordinal one. (Contributed by NM, 23-Apr-2004.) |
⊢ (𝐴 ∈ 𝑉 → {𝐴} ≈ 1o) | ||
Theorem | enpr1g 8574 | {𝐴, 𝐴} has only one element. (Contributed by FL, 15-Feb-2010.) |
⊢ (𝐴 ∈ 𝑉 → {𝐴, 𝐴} ≈ 1o) | ||
Theorem | en1 8575* | A set is equinumerous to ordinal one iff it is a singleton. (Contributed by NM, 25-Jul-2004.) |
⊢ (𝐴 ≈ 1o ↔ ∃𝑥 𝐴 = {𝑥}) | ||
Theorem | en1b 8576 | A set is equinumerous to ordinal one iff it is a singleton. (Contributed by Mario Carneiro, 17-Jan-2015.) |
⊢ (𝐴 ≈ 1o ↔ 𝐴 = {∪ 𝐴}) | ||
Theorem | reuen1 8577* | Two ways to express "exactly one". (Contributed by Stefan O'Rear, 28-Oct-2014.) |
⊢ (∃!𝑥 ∈ 𝐴 𝜑 ↔ {𝑥 ∈ 𝐴 ∣ 𝜑} ≈ 1o) | ||
Theorem | euen1 8578 | Two ways to express "exactly one". (Contributed by Stefan O'Rear, 28-Oct-2014.) |
⊢ (∃!𝑥𝜑 ↔ {𝑥 ∣ 𝜑} ≈ 1o) | ||
Theorem | euen1b 8579* | Two ways to express "𝐴 has a unique element". (Contributed by Mario Carneiro, 9-Apr-2015.) |
⊢ (𝐴 ≈ 1o ↔ ∃!𝑥 𝑥 ∈ 𝐴) | ||
Theorem | en1uniel 8580 | A singleton contains its sole element. (Contributed by Stefan O'Rear, 16-Aug-2015.) |
⊢ (𝑆 ≈ 1o → ∪ 𝑆 ∈ 𝑆) | ||
Theorem | 2dom 8581* | A set that dominates ordinal 2 has at least 2 different members. (Contributed by NM, 25-Jul-2004.) |
⊢ (2o ≼ 𝐴 → ∃𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐴 ¬ 𝑥 = 𝑦) | ||
Theorem | fundmen 8582 | A function is equinumerous to its domain. Exercise 4 of [Suppes] p. 98. (Contributed by NM, 28-Jul-2004.) (Revised by Mario Carneiro, 15-Nov-2014.) |
⊢ 𝐹 ∈ V ⇒ ⊢ (Fun 𝐹 → dom 𝐹 ≈ 𝐹) | ||
Theorem | fundmeng 8583 | A function is equinumerous to its domain. Exercise 4 of [Suppes] p. 98. (Contributed by NM, 17-Sep-2013.) |
⊢ ((𝐹 ∈ 𝑉 ∧ Fun 𝐹) → dom 𝐹 ≈ 𝐹) | ||
Theorem | cnven 8584 | A relational set is equinumerous to its converse. (Contributed by Mario Carneiro, 28-Dec-2014.) |
⊢ ((Rel 𝐴 ∧ 𝐴 ∈ 𝑉) → 𝐴 ≈ ◡𝐴) | ||
Theorem | cnvct 8585 | If a set is countable, so is its converse. (Contributed by Thierry Arnoux, 29-Dec-2016.) |
⊢ (𝐴 ≼ ω → ◡𝐴 ≼ ω) | ||
Theorem | fndmeng 8586 | A function is equinumerate to its domain. (Contributed by Paul Chapman, 22-Jun-2011.) |
⊢ ((𝐹 Fn 𝐴 ∧ 𝐴 ∈ 𝐶) → 𝐴 ≈ 𝐹) | ||
Theorem | mapsnend 8587 | Set exponentiation to a singleton exponent is equinumerous to its base. Exercise 4.43 of [Mendelson] p. 255. (Contributed by NM, 17-Dec-2003.) (Revised by Mario Carneiro, 15-Nov-2014.) (Revised by Glauco Siliprandi, 24-Dec-2020.) |
⊢ (𝜑 → 𝐴 ∈ 𝑉) & ⊢ (𝜑 → 𝐵 ∈ 𝑊) ⇒ ⊢ (𝜑 → (𝐴 ↑m {𝐵}) ≈ 𝐴) | ||
Theorem | mapsnen 8588 | Set exponentiation to a singleton exponent is equinumerous to its base. Exercise 4.43 of [Mendelson] p. 255. (Contributed by NM, 17-Dec-2003.) (Revised by Mario Carneiro, 15-Nov-2014.) (Proof shortened by AV, 17-Jul-2022.) |
⊢ 𝐴 ∈ V & ⊢ 𝐵 ∈ V ⇒ ⊢ (𝐴 ↑m {𝐵}) ≈ 𝐴 | ||
Theorem | snmapen 8589 | Set exponentiation: a singleton to any set is equinumerous to that singleton. (Contributed by NM, 17-Dec-2003.) (Revised by AV, 17-Jul-2022.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → ({𝐴} ↑m 𝐵) ≈ {𝐴}) | ||
Theorem | snmapen1 8590 | Set exponentiation: a singleton to any set is equinumerous to ordinal 1. (Proposed by BJ, 17-Jul-2022.) (Contributed by AV, 17-Jul-2022.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → ({𝐴} ↑m 𝐵) ≈ 1o) | ||
Theorem | map1 8591 | Set exponentiation: ordinal 1 to any set is equinumerous to ordinal 1. Exercise 4.42(b) of [Mendelson] p. 255. (Contributed by NM, 17-Dec-2003.) (Proof shortened by AV, 17-Jul-2022.) |
⊢ (𝐴 ∈ 𝑉 → (1o ↑m 𝐴) ≈ 1o) | ||
Theorem | en2sn 8592 | Two singletons are equinumerous. (Contributed by NM, 9-Nov-2003.) |
⊢ ((𝐴 ∈ 𝐶 ∧ 𝐵 ∈ 𝐷) → {𝐴} ≈ {𝐵}) | ||
Theorem | snfi 8593 | A singleton is finite. (Contributed by NM, 4-Nov-2002.) |
⊢ {𝐴} ∈ Fin | ||
Theorem | fiprc 8594 | The class of finite sets is a proper class. (Contributed by Jeff Hankins, 3-Oct-2008.) |
⊢ Fin ∉ V | ||
Theorem | unen 8595 | Equinumerosity of union of disjoint sets. Theorem 4 of [Suppes] p. 92. (Contributed by NM, 11-Jun-1998.) (Revised by Mario Carneiro, 26-Apr-2015.) |
⊢ (((𝐴 ≈ 𝐵 ∧ 𝐶 ≈ 𝐷) ∧ ((𝐴 ∩ 𝐶) = ∅ ∧ (𝐵 ∩ 𝐷) = ∅)) → (𝐴 ∪ 𝐶) ≈ (𝐵 ∪ 𝐷)) | ||
Theorem | enpr2d 8596 | A pair with distinct elements is equinumerous to ordinal two. (Contributed by Rohan Ridenour, 3-Aug-2023.) |
⊢ (𝜑 → 𝐴 ∈ 𝐶) & ⊢ (𝜑 → 𝐵 ∈ 𝐷) & ⊢ (𝜑 → ¬ 𝐴 = 𝐵) ⇒ ⊢ (𝜑 → {𝐴, 𝐵} ≈ 2o) | ||
Theorem | ssct 8597 | Any subset of a countable set is countable. (Contributed by Thierry Arnoux, 31-Jan-2017.) |
⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ≼ ω) → 𝐴 ≼ ω) | ||
Theorem | difsnen 8598 | All decrements of a set are equinumerous. (Contributed by Stefan O'Rear, 19-Feb-2015.) |
⊢ ((𝑋 ∈ 𝑉 ∧ 𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋) → (𝑋 ∖ {𝐴}) ≈ (𝑋 ∖ {𝐵})) | ||
Theorem | domdifsn 8599 | Dominance over a set with one element removed. (Contributed by Stefan O'Rear, 19-Feb-2015.) (Revised by Mario Carneiro, 24-Jun-2015.) |
⊢ (𝐴 ≺ 𝐵 → 𝐴 ≼ (𝐵 ∖ {𝐶})) | ||
Theorem | xpsnen 8600 | A set is equinumerous to its Cartesian product with a singleton. Proposition 4.22(c) of [Mendelson] p. 254. (Contributed by NM, 4-Jan-2004.) (Revised by Mario Carneiro, 15-Nov-2014.) |
⊢ 𝐴 ∈ V & ⊢ 𝐵 ∈ V ⇒ ⊢ (𝐴 × {𝐵}) ≈ 𝐴 |
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