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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | iccpartipre 43601 | If there is a partition, then all intermediate points are real numbers. (Contributed by AV, 11-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) & ⊢ (𝜑 → 𝐼 ∈ (1..^𝑀)) ⇒ ⊢ (𝜑 → (𝑃‘𝐼) ∈ ℝ) | ||
Theorem | iccpartiltu 43602* | If there is a partition, then all intermediate points are strictly less than the upper bound. (Contributed by AV, 12-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (1..^𝑀)(𝑃‘𝑖) < (𝑃‘𝑀)) | ||
Theorem | iccpartigtl 43603* | If there is a partition, then all intermediate points are strictly greater than the lower bound. (Contributed by AV, 12-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (1..^𝑀)(𝑃‘0) < (𝑃‘𝑖)) | ||
Theorem | iccpartlt 43604 | If there is a partition, then the lower bound is strictly less than the upper bound. Corresponds to fourierdlem11 42423 in GS's mathbox. (Contributed by AV, 12-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → (𝑃‘0) < (𝑃‘𝑀)) | ||
Theorem | iccpartltu 43605* | If there is a partition, then all intermediate points and the lower bound are strictly less than the upper bound. (Contributed by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (0..^𝑀)(𝑃‘𝑖) < (𝑃‘𝑀)) | ||
Theorem | iccpartgtl 43606* | If there is a partition, then all intermediate points and the upper bound are strictly greater than the lower bound. (Contributed by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (1...𝑀)(𝑃‘0) < (𝑃‘𝑖)) | ||
Theorem | iccpartgt 43607* | If there is a partition, then all intermediate points and the bounds are strictly ordered. (Contributed by AV, 18-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (0...𝑀)∀𝑗 ∈ (0...𝑀)(𝑖 < 𝑗 → (𝑃‘𝑖) < (𝑃‘𝑗))) | ||
Theorem | iccpartleu 43608* | If there is a partition, then all intermediate points and the lower and the upper bound are less than or equal to the upper bound. (Contributed by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (0...𝑀)(𝑃‘𝑖) ≤ (𝑃‘𝑀)) | ||
Theorem | iccpartgel 43609* | If there is a partition, then all intermediate points and the upper and the lower bound are greater than or equal to the lower bound. (Contributed by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ∀𝑖 ∈ (0...𝑀)(𝑃‘0) ≤ (𝑃‘𝑖)) | ||
Theorem | iccpartrn 43610 | If there is a partition, then all intermediate points and bounds are contained in a closed interval of extended reals. (Contributed by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ran 𝑃 ⊆ ((𝑃‘0)[,](𝑃‘𝑀))) | ||
Theorem | iccpartf 43611 | The range of the partition is between its starting point and its ending point. Corresponds to fourierdlem15 42427 in GS's mathbox. (Contributed by Glauco Siliprandi, 11-Dec-2019.) (Revised by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → 𝑃:(0...𝑀)⟶((𝑃‘0)[,](𝑃‘𝑀))) | ||
Theorem | iccpartel 43612 | If there is a partition, then all intermediate points and bounds are contained in a closed interval of extended reals. (Contributed by AV, 14-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ ((𝜑 ∧ 𝐼 ∈ (0...𝑀)) → (𝑃‘𝐼) ∈ ((𝑃‘0)[,](𝑃‘𝑀))) | ||
Theorem | iccelpart 43613* | An element of any partitioned half-open interval of extended reals is an element of a part of this partition. (Contributed by AV, 18-Jul-2020.) |
⊢ (𝑀 ∈ ℕ → ∀𝑝 ∈ (RePart‘𝑀)(𝑋 ∈ ((𝑝‘0)[,)(𝑝‘𝑀)) → ∃𝑖 ∈ (0..^𝑀)𝑋 ∈ ((𝑝‘𝑖)[,)(𝑝‘(𝑖 + 1))))) | ||
Theorem | iccpartiun 43614* | A half-open interval of extended reals is the union of the parts of its partition. (Contributed by AV, 18-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ((𝑃‘0)[,)(𝑃‘𝑀)) = ∪ 𝑖 ∈ (0..^𝑀)((𝑃‘𝑖)[,)(𝑃‘(𝑖 + 1)))) | ||
Theorem | icceuelpartlem 43615 | Lemma for icceuelpart 43616. (Contributed by AV, 19-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → ((𝐼 ∈ (0..^𝑀) ∧ 𝐽 ∈ (0..^𝑀)) → (𝐼 < 𝐽 → (𝑃‘(𝐼 + 1)) ≤ (𝑃‘𝐽)))) | ||
Theorem | icceuelpart 43616* | An element of a partitioned half-open interval of extended reals is an element of exactly one part of the partition. (Contributed by AV, 19-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ ((𝜑 ∧ 𝑋 ∈ ((𝑃‘0)[,)(𝑃‘𝑀))) → ∃!𝑖 ∈ (0..^𝑀)𝑋 ∈ ((𝑃‘𝑖)[,)(𝑃‘(𝑖 + 1)))) | ||
Theorem | iccpartdisj 43617* | The segments of a partitioned half-open interval of extended reals are a disjoint collection. (Contributed by AV, 19-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) ⇒ ⊢ (𝜑 → Disj 𝑖 ∈ (0..^𝑀)((𝑃‘𝑖)[,)(𝑃‘(𝑖 + 1)))) | ||
Theorem | iccpartnel 43618 | A point of a partition is not an element of any open interval determined by the partition. Corresponds to fourierdlem12 42424 in GS's mathbox. (Contributed by Glauco Siliprandi, 11-Dec-2019.) (Revised by AV, 8-Jul-2020.) |
⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑃 ∈ (RePart‘𝑀)) & ⊢ (𝜑 → 𝑋 ∈ ran 𝑃) ⇒ ⊢ ((𝜑 ∧ 𝐼 ∈ (0..^𝑀)) → ¬ 𝑋 ∈ ((𝑃‘𝐼)(,)(𝑃‘(𝐼 + 1)))) | ||
Theorem | fargshiftfv 43619* | If a class is a function, then the values of the "shifted function" correspond to the function values of the class. (Contributed by Alexander van der Vekens, 23-Nov-2017.) |
⊢ 𝐺 = (𝑥 ∈ (0..^(♯‘𝐹)) ↦ (𝐹‘(𝑥 + 1))) ⇒ ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐹:(1...𝑁)⟶dom 𝐸) → (𝑋 ∈ (0..^𝑁) → (𝐺‘𝑋) = (𝐹‘(𝑋 + 1)))) | ||
Theorem | fargshiftf 43620* | If a class is a function, then also its "shifted function" is a function. (Contributed by Alexander van der Vekens, 23-Nov-2017.) |
⊢ 𝐺 = (𝑥 ∈ (0..^(♯‘𝐹)) ↦ (𝐹‘(𝑥 + 1))) ⇒ ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐹:(1...𝑁)⟶dom 𝐸) → 𝐺:(0..^(♯‘𝐹))⟶dom 𝐸) | ||
Theorem | fargshiftf1 43621* | If a function is 1-1, then also the shifted function is 1-1. (Contributed by Alexander van der Vekens, 23-Nov-2017.) |
⊢ 𝐺 = (𝑥 ∈ (0..^(♯‘𝐹)) ↦ (𝐹‘(𝑥 + 1))) ⇒ ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐹:(1...𝑁)–1-1→dom 𝐸) → 𝐺:(0..^(♯‘𝐹))–1-1→dom 𝐸) | ||
Theorem | fargshiftfo 43622* | If a function is onto, then also the shifted function is onto. (Contributed by Alexander van der Vekens, 24-Nov-2017.) |
⊢ 𝐺 = (𝑥 ∈ (0..^(♯‘𝐹)) ↦ (𝐹‘(𝑥 + 1))) ⇒ ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐹:(1...𝑁)–onto→dom 𝐸) → 𝐺:(0..^(♯‘𝐹))–onto→dom 𝐸) | ||
Theorem | fargshiftfva 43623* | The values of a shifted function correspond to the value of the original function. (Contributed by Alexander van der Vekens, 24-Nov-2017.) |
⊢ 𝐺 = (𝑥 ∈ (0..^(♯‘𝐹)) ↦ (𝐹‘(𝑥 + 1))) ⇒ ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐹:(1...𝑁)⟶dom 𝐸) → (∀𝑘 ∈ (1...𝑁)(𝐸‘(𝐹‘𝑘)) = ⦋𝑘 / 𝑥⦌𝑃 → ∀𝑙 ∈ (0..^𝑁)(𝐸‘(𝐺‘𝑙)) = ⦋(𝑙 + 1) / 𝑥⦌𝑃)) | ||
Theorem | lswn0 43624 | The last symbol of a not empty word exists. The empty set must be excluded as symbol, because otherwise, it cannot be distinguished between valid cases (∅ is the last symbol) and invalid cases (∅ means that no last symbol exists. This is because of the special definition of a function in set.mm. (Contributed by Alexander van der Vekens, 18-Mar-2018.) |
⊢ ((𝑊 ∈ Word 𝑉 ∧ ∅ ∉ 𝑉 ∧ (♯‘𝑊) ≠ 0) → (lastS‘𝑊) ≠ ∅) | ||
Syntax | wich 43625 | Extend wff notation to include the propery of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable. Read this notation as "𝑥 and 𝑦 are interchangeable in wff 𝜑". |
wff [𝑥⇄𝑦]𝜑 | ||
Definition | df-ich 43626* | Define the propery of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable. For an alternate definition using implicit substitution and a temporary setvar variable see ichcircshi 43632. Another, equivalent definition using two temporary setvar variables is provided in dfich2 43633. (Contributed by AV, 29-Jul-2023.) |
⊢ ([𝑥⇄𝑦]𝜑 ↔ ∀𝑥∀𝑦([𝑥 / 𝑎][𝑦 / 𝑥][𝑎 / 𝑦]𝜑 ↔ 𝜑)) | ||
Theorem | nfich1 43627 | The first interchangeable setvar variable is not free. (Contributed by AV, 21-Aug-2023.) |
⊢ Ⅎ𝑥[𝑥⇄𝑦]𝜑 | ||
Theorem | nfich2 43628 | The second interchangeable setvar variable is not free. (Contributed by AV, 21-Aug-2023.) |
⊢ Ⅎ𝑦[𝑥⇄𝑦]𝜑 | ||
Theorem | ichv 43629* | Setvar variables are interchangeable in a wff they do not appear in. (Contributed by SN, 23-Nov-2023.) |
⊢ [𝑥⇄𝑦]𝜑 | ||
Theorem | ichf 43630 | Setvar variables are interchangeable in a wff they are not free in. (Contributed by SN, 23-Nov-2023.) |
⊢ Ⅎ𝑥𝜑 & ⊢ Ⅎ𝑦𝜑 ⇒ ⊢ [𝑥⇄𝑦]𝜑 | ||
Theorem | ichid 43631 | A setvar variable is always interchangeable with itself. (Contributed by AV, 29-Jul-2023.) |
⊢ [𝑥⇄𝑥]𝜑 | ||
Theorem | ichcircshi 43632* | The setvar variables are interchangeable if they can be circularily shifted using a third setvar variable, using implicit substitution. (Contributed by AV, 29-Jul-2023.) |
⊢ (𝑥 = 𝑧 → (𝜑 ↔ 𝜓)) & ⊢ (𝑦 = 𝑥 → (𝜓 ↔ 𝜒)) & ⊢ (𝑧 = 𝑦 → (𝜒 ↔ 𝜑)) ⇒ ⊢ [𝑥⇄𝑦]𝜑 | ||
Theorem | dfich2 43633* | Alternate definition of the propery of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable. (Contributed by AV and WL, 6-Aug-2023.) |
⊢ ([𝑥⇄𝑦]𝜑 ↔ ∀𝑎∀𝑏([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑥][𝑎 / 𝑦]𝜑)) | ||
Theorem | dfich2ai 43634* | Obsolete version of dfich2 43633 as of 18-Sep-2023. The definition df-ich 43626 of the propery of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable implies the alternate definition dfich2 43633. (Contributed by AV, 6-Aug-2023.) (New usage is discouraged.) (Proof modification is discouraged.) |
⊢ (∀𝑥∀𝑦([𝑥 / 𝑧][𝑦 / 𝑥][𝑧 / 𝑦]𝜑 ↔ 𝜑) → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑥][𝑎 / 𝑦]𝜑)) | ||
Theorem | dfich2bi 43635* | Obsolete version of dfich2 43633 as of 18-Sep-2023. The alternate definition dfich2 43633 of the propery of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable implies the definition df-ich 43626. (Contributed by AV, 6-Aug-2023.) (New usage is discouraged.) (Proof modification is discouraged.) |
⊢ (∀𝑎∀𝑏([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑥][𝑎 / 𝑦]𝜑) → ([𝑥 / 𝑧][𝑦 / 𝑥][𝑧 / 𝑦]𝜑 ↔ 𝜑)) | ||
Theorem | dfich2OLD 43636* | Obsolete version of dfich2 43633 as of 18-Sep-2023. Alternate definition of the propery of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable. (Contributed by AV, 6-Aug-2023.) (New usage is discouraged.) (Proof modification is discouraged.) |
⊢ ([𝑥⇄𝑦]𝜑 ↔ ∀𝑎∀𝑏([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑥][𝑎 / 𝑦]𝜑)) | ||
Theorem | ichcom 43637* | The interchangeability of setvar variables is commutative. (Contributed by AV, 20-Aug-2023.) |
⊢ ([𝑥⇄𝑦]𝜓 ↔ [𝑦⇄𝑥]𝜓) | ||
Theorem | ichbi12i 43638* | Equivalence for interchangeable setvar variables. (Contributed by AV, 29-Jul-2023.) |
⊢ ((𝑥 = 𝑎 ∧ 𝑦 = 𝑏) → (𝜓 ↔ 𝜒)) ⇒ ⊢ ([𝑥⇄𝑦]𝜓 ↔ [𝑎⇄𝑏]𝜒) | ||
Theorem | icheqid 43639 | In an equality for the same setvar variable, the setvar variable is interchangeable by itself. Special case of ichid 43631 and icheq 43640 without distinct variables restriction. (Contributed by AV, 29-Jul-2023.) |
⊢ [𝑥⇄𝑥]𝑥 = 𝑥 | ||
Theorem | icheq 43640* | In an equality of setvar variables, the setvar variables are interchangeable. (Contributed by AV, 29-Jul-2023.) |
⊢ [𝑥⇄𝑦]𝑥 = 𝑦 | ||
Theorem | ichnfimlem1 43641* | Lemma for ichnfimlem3 43643: A substitution of a non-free variable has no effect. Give the distinctor in a form that can be easily eliminiated. (Contributed by Wolf Lammen, 6-Aug-2023.) |
⊢ ((∀𝑦Ⅎ𝑥𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑦]𝜑)) | ||
Theorem | ichnfimlem2 43642* | Lemma for ichnfimlem3 43643: When substituting successively for two always equal variables, the second substitution has no effect. (Contributed by Wolf Lammen, 6-Aug-2023.) |
⊢ (∀𝑥 𝑥 = 𝑦 → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑦]𝜑)) | ||
Theorem | ichnfimlem3 43643* | Lemma for ichnfim 43644: A substitution of a non-free variable has no effect. (Contributed by Wolf Lammen, 6-Aug-2023.) |
⊢ (∀𝑦Ⅎ𝑥𝜑 → ([𝑎 / 𝑥][𝑏 / 𝑦]𝜑 ↔ [𝑏 / 𝑦]𝜑)) | ||
Theorem | ichnfim 43644* | If in an interchangeability context 𝑥 is not free in 𝜑, the same holds for 𝑦. (Contributed by Wolf Lammen, 6-Aug-2023.) (Revised by AV, 23-Sep-2023.) |
⊢ ((∀𝑦Ⅎ𝑥𝜑 ∧ [𝑥⇄𝑦]𝜑) → ∀𝑥Ⅎ𝑦𝜑) | ||
Theorem | ichnfb 43645* | If 𝑥 and 𝑦 are interchangeable in 𝜑, they are both free or both not free in 𝜑. (Contributed by Wolf Lammen, 6-Aug-2023.) (Revised by AV, 23-Sep-2023.) |
⊢ ([𝑥⇄𝑦]𝜑 → (∀𝑥Ⅎ𝑦𝜑 ↔ ∀𝑦Ⅎ𝑥𝜑)) | ||
Theorem | ichn 43646 | Negation does not affect interchangability. (Contributed by SN, 30-Aug-2023.) |
⊢ ([𝑎⇄𝑏]𝜑 ↔ [𝑎⇄𝑏] ¬ 𝜑) | ||
Theorem | ichal 43647* | Move a universal quantifier inside interchangability. (Contributed by SN, 30-Aug-2023.) |
⊢ (∀𝑥[𝑎⇄𝑏]𝜑 → [𝑎⇄𝑏]∀𝑥𝜑) | ||
Theorem | ich2al 43648 | Two setvar variables are always interchangeable when there are two universal quantifiers. (Contributed by SN, 23-Nov-2023.) |
⊢ [𝑥⇄𝑦]∀𝑥∀𝑦𝜑 | ||
Theorem | ich2ex 43649 | Two setvar variables are always interchangeable when there are two existential quantifiers. (Contributed by SN, 23-Nov-2023.) |
⊢ [𝑥⇄𝑦]∃𝑥∃𝑦𝜑 | ||
Theorem | ichan 43650* | If two setvar variables are interchangeable in two wffs, then they are interchangeable in the conjunction of these two wffs. Notice that the reverse implication is not necessarily true. Corresponding theorems will hold for other commutative operations, too. (Contributed by AV, 31-Jul-2023.) |
⊢ (([𝑎⇄𝑏]𝜑 ∧ [𝑎⇄𝑏]𝜓) → [𝑎⇄𝑏](𝜑 ∧ 𝜓)) | ||
Theorem | ichexmpl1 43651* | Example for interchangeable setvar variables in a statement of predicate calculus with equality. (Contributed by AV, 31-Jul-2023.) |
⊢ [𝑎⇄𝑏]∃𝑎∃𝑏∃𝑐(𝑎 = 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑏 ≠ 𝑐) | ||
Theorem | ichexmpl2 43652* | Example for interchangeable setvar variables in an arithmetic expression. (Contributed by AV, 31-Jul-2023.) |
⊢ [𝑎⇄𝑏]((𝑎 ∈ ℂ ∧ 𝑏 ∈ ℂ ∧ 𝑐 ∈ ℂ) → ((𝑎↑2) + (𝑏↑2)) = (𝑐↑2)) | ||
Theorem | ich2exprop 43653* | If the setvar variables are interchangeable in a wff, there is an ordered pair fulfilling the wff iff there is an unordered pair fulfilling the wff. (Contributed by AV, 16-Jul-2023.) |
⊢ ((𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋 ∧ [𝑎⇄𝑏]𝜑) → (∃𝑎∃𝑏({𝐴, 𝐵} = {𝑎, 𝑏} ∧ 𝜑) ↔ ∃𝑎∃𝑏(〈𝐴, 𝐵〉 = 〈𝑎, 𝑏〉 ∧ 𝜑))) | ||
Theorem | ichnreuop 43654* | If the setvar variables are interchangeable in a wff, there is never a unique ordered pair with different components fulfilling the wff (because if 〈𝑎, 𝑏〉 fulfils the wff, then also 〈𝑏, 𝑎〉 fulfils the wff). (Contributed by AV, 27-Aug-2023.) |
⊢ ([𝑎⇄𝑏]𝜑 → ¬ ∃!𝑝 ∈ (𝑋 × 𝑋)∃𝑎∃𝑏(𝑝 = 〈𝑎, 𝑏〉 ∧ 𝑎 ≠ 𝑏 ∧ 𝜑)) | ||
Theorem | ichreuopeq 43655* | If the setvar variables are interchangeable in a wff, and there is a unique ordered pair fulfilling the wff, then both setvar variables must be equal. (Contributed by AV, 28-Aug-2023.) |
⊢ ([𝑎⇄𝑏]𝜑 → (∃!𝑝 ∈ (𝑋 × 𝑋)∃𝑎∃𝑏(𝑝 = 〈𝑎, 𝑏〉 ∧ 𝜑) → ∃𝑎∃𝑏(𝑎 = 𝑏 ∧ 𝜑))) | ||
Theorem | sprid 43656 | Two identical representations of the class of all unordered pairs. (Contributed by AV, 21-Nov-2021.) |
⊢ {𝑝 ∣ ∃𝑎 ∈ V ∃𝑏 ∈ V 𝑝 = {𝑎, 𝑏}} = {𝑝 ∣ ∃𝑎∃𝑏 𝑝 = {𝑎, 𝑏}} | ||
Theorem | elsprel 43657* | An unordered pair is an element of all unordered pairs. At least one of the two elements of the unordered pair must be a set. Otherwise, the unordered pair would be the empty set, see prprc 4703, which is not an element of all unordered pairs, see spr0nelg 43658. (Contributed by AV, 21-Nov-2021.) |
⊢ ((𝐴 ∈ 𝑉 ∨ 𝐵 ∈ 𝑊) → {𝐴, 𝐵} ∈ {𝑝 ∣ ∃𝑎∃𝑏 𝑝 = {𝑎, 𝑏}}) | ||
Theorem | spr0nelg 43658* | The empty set is not an element of all unordered pairs. (Contributed by AV, 21-Nov-2021.) |
⊢ ∅ ∉ {𝑝 ∣ ∃𝑎∃𝑏 𝑝 = {𝑎, 𝑏}} | ||
Syntax | cspr 43659 | Extend class notation with set of pairs. |
class Pairs | ||
Definition | df-spr 43660* | Define the function which maps a set 𝑣 to the set of pairs consisting of elements of the set 𝑣. (Contributed by AV, 21-Nov-2021.) |
⊢ Pairs = (𝑣 ∈ V ↦ {𝑝 ∣ ∃𝑎 ∈ 𝑣 ∃𝑏 ∈ 𝑣 𝑝 = {𝑎, 𝑏}}) | ||
Theorem | sprval 43661* | The set of all unordered pairs over a given set 𝑉. (Contributed by AV, 21-Nov-2021.) |
⊢ (𝑉 ∈ 𝑊 → (Pairs‘𝑉) = {𝑝 ∣ ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 𝑝 = {𝑎, 𝑏}}) | ||
Theorem | sprvalpw 43662* | The set of all unordered pairs over a given set 𝑉, expressed by a restricted class abstraction. (Contributed by AV, 21-Nov-2021.) |
⊢ (𝑉 ∈ 𝑊 → (Pairs‘𝑉) = {𝑝 ∈ 𝒫 𝑉 ∣ ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 𝑝 = {𝑎, 𝑏}}) | ||
Theorem | sprssspr 43663* | The set of all unordered pairs over a given set 𝑉 is a subset of the set of all unordered pairs. (Contributed by AV, 21-Nov-2021.) |
⊢ (Pairs‘𝑉) ⊆ {𝑝 ∣ ∃𝑎∃𝑏 𝑝 = {𝑎, 𝑏}} | ||
Theorem | spr0el 43664 | The empty set is not an unordered pair over any set 𝑉. (Contributed by AV, 21-Nov-2021.) |
⊢ ∅ ∉ (Pairs‘𝑉) | ||
Theorem | sprvalpwn0 43665* | The set of all unordered pairs over a given set 𝑉, expressed by a restricted class abstraction. (Contributed by AV, 21-Nov-2021.) |
⊢ (𝑉 ∈ 𝑊 → (Pairs‘𝑉) = {𝑝 ∈ (𝒫 𝑉 ∖ {∅}) ∣ ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 𝑝 = {𝑎, 𝑏}}) | ||
Theorem | sprel 43666* | An element of the set of all unordered pairs over a given set 𝑉 is a pair of elements of the set 𝑉. (Contributed by AV, 22-Nov-2021.) |
⊢ (𝑋 ∈ (Pairs‘𝑉) → ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 𝑋 = {𝑎, 𝑏}) | ||
Theorem | prssspr 43667* | An element of a subset of the set of all unordered pairs over a given set 𝑉, is a pair of elements of the set 𝑉. (Contributed by AV, 22-Nov-2021.) |
⊢ ((𝑃 ⊆ (Pairs‘𝑉) ∧ 𝑋 ∈ 𝑃) → ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 𝑋 = {𝑎, 𝑏}) | ||
Theorem | prelspr 43668 | An unordered pair of elements of a fixed set 𝑉 belongs to the set of all unordered pairs over the set 𝑉. (Contributed by AV, 21-Nov-2021.) |
⊢ ((𝑉 ∈ 𝑊 ∧ (𝑋 ∈ 𝑉 ∧ 𝑌 ∈ 𝑉)) → {𝑋, 𝑌} ∈ (Pairs‘𝑉)) | ||
Theorem | prsprel 43669 | The elements of a pair from the set of all unordered pairs over a given set 𝑉 are elements of the set 𝑉. (Contributed by AV, 22-Nov-2021.) |
⊢ (({𝑋, 𝑌} ∈ (Pairs‘𝑉) ∧ (𝑋 ∈ 𝑈 ∧ 𝑌 ∈ 𝑊)) → (𝑋 ∈ 𝑉 ∧ 𝑌 ∈ 𝑉)) | ||
Theorem | prsssprel 43670 | The elements of a pair from a subset of the set of all unordered pairs over a given set 𝑉 are elements of the set 𝑉. (Contributed by AV, 21-Nov-2021.) |
⊢ ((𝑃 ⊆ (Pairs‘𝑉) ∧ {𝑋, 𝑌} ∈ 𝑃 ∧ (𝑋 ∈ 𝑈 ∧ 𝑌 ∈ 𝑊)) → (𝑋 ∈ 𝑉 ∧ 𝑌 ∈ 𝑉)) | ||
Theorem | sprvalpwle2 43671* | The set of all unordered pairs over a given set 𝑉, expressed by a restricted class abstraction. (Contributed by AV, 24-Nov-2021.) |
⊢ (𝑉 ∈ 𝑊 → (Pairs‘𝑉) = {𝑝 ∈ (𝒫 𝑉 ∖ {∅}) ∣ (♯‘𝑝) ≤ 2}) | ||
Theorem | sprsymrelfvlem 43672* | Lemma for sprsymrelf 43677 and sprsymrelfv 43676. (Contributed by AV, 19-Nov-2021.) |
⊢ (𝑃 ⊆ (Pairs‘𝑉) → {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑃 𝑐 = {𝑥, 𝑦}} ∈ 𝒫 (𝑉 × 𝑉)) | ||
Theorem | sprsymrelf1lem 43673* | Lemma for sprsymrelf1 43678. (Contributed by AV, 22-Nov-2021.) |
⊢ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) → ({〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}} → 𝑎 ⊆ 𝑏)) | ||
Theorem | sprsymrelfolem1 43674* | Lemma 1 for sprsymrelfo 43679. (Contributed by AV, 22-Nov-2021.) |
⊢ 𝑄 = {𝑞 ∈ (Pairs‘𝑉) ∣ ∀𝑎 ∈ 𝑉 ∀𝑏 ∈ 𝑉 (𝑞 = {𝑎, 𝑏} → 𝑎𝑅𝑏)} ⇒ ⊢ 𝑄 ∈ 𝒫 (Pairs‘𝑉) | ||
Theorem | sprsymrelfolem2 43675* | Lemma 2 for sprsymrelfo 43679. (Contributed by AV, 23-Nov-2021.) |
⊢ 𝑄 = {𝑞 ∈ (Pairs‘𝑉) ∣ ∀𝑎 ∈ 𝑉 ∀𝑏 ∈ 𝑉 (𝑞 = {𝑎, 𝑏} → 𝑎𝑅𝑏)} ⇒ ⊢ ((𝑉 ∈ 𝑊 ∧ 𝑅 ⊆ (𝑉 × 𝑉) ∧ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑅𝑦 ↔ 𝑦𝑅𝑥)) → (𝑥𝑅𝑦 ↔ ∃𝑐 ∈ 𝑄 𝑐 = {𝑥, 𝑦})) | ||
Theorem | sprsymrelfv 43676* | The value of the function 𝐹 which maps a subset of the set of pairs over a fixed set 𝑉 to the relation relating two elements of the set 𝑉 iff they are in a pair of the subset. (Contributed by AV, 19-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑝 𝑐 = {𝑥, 𝑦}}) ⇒ ⊢ (𝑋 ∈ 𝑃 → (𝐹‘𝑋) = {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑋 𝑐 = {𝑥, 𝑦}}) | ||
Theorem | sprsymrelf 43677* | The mapping 𝐹 is a function from the subsets of the set of pairs over a fixed set 𝑉 into the symmetric relations 𝑅 on the fixed set 𝑉. (Contributed by AV, 19-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑝 𝑐 = {𝑥, 𝑦}}) ⇒ ⊢ 𝐹:𝑃⟶𝑅 | ||
Theorem | sprsymrelf1 43678* | The mapping 𝐹 is a one-to-one function from the subsets of the set of pairs over a fixed set 𝑉 into the symmetric relations 𝑅 on the fixed set 𝑉. (Contributed by AV, 19-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑝 𝑐 = {𝑥, 𝑦}}) ⇒ ⊢ 𝐹:𝑃–1-1→𝑅 | ||
Theorem | sprsymrelfo 43679* | The mapping 𝐹 is a function from the subsets of the set of pairs over a fixed set 𝑉 onto the symmetric relations 𝑅 on the fixed set 𝑉. (Contributed by AV, 23-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑝 𝑐 = {𝑥, 𝑦}}) ⇒ ⊢ (𝑉 ∈ 𝑊 → 𝐹:𝑃–onto→𝑅) | ||
Theorem | sprsymrelf1o 43680* | The mapping 𝐹 is a bijection between the subsets of the set of pairs over a fixed set 𝑉 into the symmetric relations 𝑅 on the fixed set 𝑉. (Contributed by AV, 23-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ {〈𝑥, 𝑦〉 ∣ ∃𝑐 ∈ 𝑝 𝑐 = {𝑥, 𝑦}}) ⇒ ⊢ (𝑉 ∈ 𝑊 → 𝐹:𝑃–1-1-onto→𝑅) | ||
Theorem | sprbisymrel 43681* | There is a bijection between the subsets of the set of pairs over a fixed set 𝑉 and the symmetric relations 𝑅 on the fixed set 𝑉. (Contributed by AV, 23-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} ⇒ ⊢ (𝑉 ∈ 𝑊 → ∃𝑓 𝑓:𝑃–1-1-onto→𝑅) | ||
Theorem | sprsymrelen 43682* | The class 𝑃 of subsets of the set of pairs over a fixed set 𝑉 and the class 𝑅 of symmetric relations on the fixed set 𝑉 are equinumerous. (Contributed by AV, 27-Nov-2021.) |
⊢ 𝑃 = 𝒫 (Pairs‘𝑉) & ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)} ⇒ ⊢ (𝑉 ∈ 𝑊 → 𝑃 ≈ 𝑅) | ||
Proper (unordered) pairs are unordered pairs with exactly 2 elements. The set of proper pairs with elements of a class 𝑉 is defined by {𝑥 ∈ 𝒫 𝑉 ∣ (♯‘𝑥) = 2}. For example, {1, 2} is a proper pair, because 1 ≠ 2 ( see 1ne2 11846). Examples for not proper unordered pairs are {1, 1} = {1} (see preqsn 4792), {1, V} = {1} (see prprc2 4702) or {V, V} = ∅ (see prprc 4703). | ||
Theorem | prpair 43683* | Characterization of a proper pair: A class is a proper pair iff it consists of exactly two different sets. (Contributed by AV, 11-Mar-2023.) |
⊢ 𝑃 = {𝑥 ∈ 𝒫 𝑉 ∣ (♯‘𝑥) = 2} ⇒ ⊢ (𝑋 ∈ 𝑃 ↔ ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 (𝑋 = {𝑎, 𝑏} ∧ 𝑎 ≠ 𝑏)) | ||
Theorem | prproropf1olem0 43684 | Lemma 0 for prproropf1o 43689. Remark: 𝑂, the set of ordered ordered pairs, i.e., ordered pairs in which the first component is less than the second component, can alternatively be written as 𝑂 = {𝑥 ∈ (𝑉 × 𝑉) ∣ (1st ‘𝑥)𝑅(2nd ‘𝑥)} or even as 𝑂 = {𝑥 ∈ (𝑉 × 𝑉) ∣ 〈(1st ‘𝑥), (2nd ‘𝑥)〉 ∈ 𝑅}, by which the relationship between ordered and unordered pair is immediately visible. (Contributed by AV, 18-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) ⇒ ⊢ (𝑊 ∈ 𝑂 ↔ (𝑊 = 〈(1st ‘𝑊), (2nd ‘𝑊)〉 ∧ ((1st ‘𝑊) ∈ 𝑉 ∧ (2nd ‘𝑊) ∈ 𝑉) ∧ (1st ‘𝑊)𝑅(2nd ‘𝑊))) | ||
Theorem | prproropf1olem1 43685* | Lemma 1 for prproropf1o 43689. (Contributed by AV, 12-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} ⇒ ⊢ ((𝑅 Or 𝑉 ∧ 𝑊 ∈ 𝑂) → {(1st ‘𝑊), (2nd ‘𝑊)} ∈ 𝑃) | ||
Theorem | prproropf1olem2 43686* | Lemma 2 for prproropf1o 43689. (Contributed by AV, 13-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} ⇒ ⊢ ((𝑅 Or 𝑉 ∧ 𝑋 ∈ 𝑃) → 〈inf(𝑋, 𝑉, 𝑅), sup(𝑋, 𝑉, 𝑅)〉 ∈ 𝑂) | ||
Theorem | prproropf1olem3 43687* | Lemma 3 for prproropf1o 43689. (Contributed by AV, 13-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ 〈inf(𝑝, 𝑉, 𝑅), sup(𝑝, 𝑉, 𝑅)〉) ⇒ ⊢ ((𝑅 Or 𝑉 ∧ 𝑊 ∈ 𝑂) → (𝐹‘{(1st ‘𝑊), (2nd ‘𝑊)}) = 〈(1st ‘𝑊), (2nd ‘𝑊)〉) | ||
Theorem | prproropf1olem4 43688* | Lemma 4 for prproropf1o 43689. (Contributed by AV, 14-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ 〈inf(𝑝, 𝑉, 𝑅), sup(𝑝, 𝑉, 𝑅)〉) ⇒ ⊢ ((𝑅 Or 𝑉 ∧ 𝑊 ∈ 𝑃 ∧ 𝑍 ∈ 𝑃) → ((𝐹‘𝑍) = (𝐹‘𝑊) → 𝑍 = 𝑊)) | ||
Theorem | prproropf1o 43689* | There is a bijection between the set of proper pairs and the set of ordered ordered pairs, i.e., ordered pairs in which the first component is less than the second component. (Contributed by AV, 15-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} & ⊢ 𝐹 = (𝑝 ∈ 𝑃 ↦ 〈inf(𝑝, 𝑉, 𝑅), sup(𝑝, 𝑉, 𝑅)〉) ⇒ ⊢ (𝑅 Or 𝑉 → 𝐹:𝑃–1-1-onto→𝑂) | ||
Theorem | prproropen 43690* | The set of proper pairs and the set of ordered ordered pairs, i.e., ordered pairs in which the first component is less than the second component, are equinumerous. (Contributed by AV, 15-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} ⇒ ⊢ ((𝑉 ∈ 𝑊 ∧ 𝑅 Or 𝑉) → 𝑂 ≈ 𝑃) | ||
Theorem | prproropreud 43691* | There is exactly one ordered ordered pair fulfilling a wff iff there is exactly one proper pair fulfilling an equivalent wff. (Contributed by AV, 20-Mar-2023.) |
⊢ 𝑂 = (𝑅 ∩ (𝑉 × 𝑉)) & ⊢ 𝑃 = {𝑝 ∈ 𝒫 𝑉 ∣ (♯‘𝑝) = 2} & ⊢ (𝜑 → 𝑅 Or 𝑉) & ⊢ (𝑥 = 〈inf(𝑦, 𝑉, 𝑅), sup(𝑦, 𝑉, 𝑅)〉 → (𝜓 ↔ 𝜒)) & ⊢ (𝑥 = 𝑧 → (𝜓 ↔ 𝜃)) ⇒ ⊢ (𝜑 → (∃!𝑥 ∈ 𝑂 𝜓 ↔ ∃!𝑦 ∈ 𝑃 𝜒)) | ||
Theorem | pairreueq 43692* | Two equivalent representations of the existence of a unique proper pair. (Contributed by AV, 1-Mar-2023.) |
⊢ 𝑃 = {𝑥 ∈ 𝒫 𝑉 ∣ (♯‘𝑥) = 2} ⇒ ⊢ (∃!𝑝 ∈ 𝑃 𝜑 ↔ ∃!𝑝 ∈ 𝒫 𝑉((♯‘𝑝) = 2 ∧ 𝜑)) | ||
Theorem | paireqne 43693* | Two sets are not equal iff there is exactly one proper pair whose elements are either one of these sets. (Contributed by AV, 27-Jan-2023.) |
⊢ (𝜑 → 𝐴 ∈ 𝑉) & ⊢ (𝜑 → 𝐵 ∈ 𝑉) & ⊢ 𝑃 = {𝑥 ∈ 𝒫 𝑉 ∣ (♯‘𝑥) = 2} ⇒ ⊢ (𝜑 → (∃!𝑝 ∈ 𝑃 ∀𝑥 ∈ 𝑝 (𝑥 = 𝐴 ∨ 𝑥 = 𝐵) ↔ 𝐴 ≠ 𝐵)) | ||
Syntax | cprpr 43694 | Extend class notation with set of proper unordered pairs. |
class Pairsproper | ||
Definition | df-prpr 43695* | Define the function which maps a set 𝑣 to the set of proper unordered pairs consisting of exactly two (different) elements of the set 𝑣. (Contributed by AV, 29-Apr-2023.) |
⊢ Pairsproper = (𝑣 ∈ V ↦ {𝑝 ∣ ∃𝑎 ∈ 𝑣 ∃𝑏 ∈ 𝑣 (𝑎 ≠ 𝑏 ∧ 𝑝 = {𝑎, 𝑏})}) | ||
Theorem | prprval 43696* | The set of all proper unordered pairs over a given set 𝑉. (Contributed by AV, 29-Apr-2023.) |
⊢ (𝑉 ∈ 𝑊 → (Pairsproper‘𝑉) = {𝑝 ∣ ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 (𝑎 ≠ 𝑏 ∧ 𝑝 = {𝑎, 𝑏})}) | ||
Theorem | prprvalpw 43697* | The set of all proper unordered pairs over a given set 𝑉, expressed by a restricted class abstraction. (Contributed by AV, 29-Apr-2023.) |
⊢ (𝑉 ∈ 𝑊 → (Pairsproper‘𝑉) = {𝑝 ∈ 𝒫 𝑉 ∣ ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 (𝑎 ≠ 𝑏 ∧ 𝑝 = {𝑎, 𝑏})}) | ||
Theorem | prprelb 43698 | An element of the set of all proper unordered pairs over a given set 𝑉 is a subset of 𝑉 of size two. (Contributed by AV, 29-Apr-2023.) |
⊢ (𝑉 ∈ 𝑊 → (𝑃 ∈ (Pairsproper‘𝑉) ↔ (𝑃 ∈ 𝒫 𝑉 ∧ (♯‘𝑃) = 2))) | ||
Theorem | prprelprb 43699* | A set is an element of the set of all proper unordered pairs over a given set 𝑋 iff it is a pair of different elements of the set 𝑋. (Contributed by AV, 7-May-2023.) |
⊢ (𝑃 ∈ (Pairsproper‘𝑋) ↔ (𝑋 ∈ V ∧ ∃𝑎 ∈ 𝑋 ∃𝑏 ∈ 𝑋 (𝑃 = {𝑎, 𝑏} ∧ 𝑎 ≠ 𝑏))) | ||
Theorem | prprspr2 43700* | The set of all proper unordered pairs over a given set 𝑉 is the set of all unordered pairs over that set of size two. (Contributed by AV, 29-Apr-2023.) |
⊢ (Pairsproper‘𝑉) = {𝑝 ∈ (Pairs‘𝑉) ∣ (♯‘𝑝) = 2} |
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