Home Intuitionistic Logic ExplorerTheorem List (p. 44 of 102) < Previous  Next > Bad symbols? Try the GIF version. Mirrors  >  Metamath Home Page  >  ILE Home Page  >  Theorem List Contents  >  Recent Proofs       This page: Page List

Theorem List for Intuitionistic Logic Explorer - 4301-4400   *Has distinct variable group(s)
TypeLabelDescription
Statement

Theoremwetriext 4301* A trichotomous well-order is extensional. (Contributed by Jim Kingdon, 26-Sep-2021.)
(𝜑𝑅 We 𝐴)    &   (𝜑𝐴𝑉)    &   (𝜑 → ∀𝑎𝐴𝑏𝐴 (𝑎𝑅𝑏𝑎 = 𝑏𝑏𝑅𝑎))    &   (𝜑𝐵𝐴)    &   (𝜑𝐶𝐴)    &   (𝜑 → ∀𝑧𝐴 (𝑧𝑅𝐵𝑧𝑅𝐶))       (𝜑𝐵 = 𝐶)

Theoremwessep 4302 A subset of a set well-ordered by set membership is well-ordered by set membership. (Contributed by Jim Kingdon, 30-Sep-2021.)
(( E We 𝐴𝐵𝐴) → E We 𝐵)

Theoremreg3exmidlemwe 4303* Lemma for reg3exmid 4304. Our counterexample 𝐴 satisfies We. (Contributed by Jim Kingdon, 3-Oct-2021.)
𝐴 = {𝑥 ∈ {∅, {∅}} ∣ (𝑥 = {∅} ∨ (𝑥 = ∅ ∧ 𝜑))}        E We 𝐴

Theoremreg3exmid 4304* If any inhabited set satisfying df-wetr 4071 for E has a minimal element, excluded middle follows. (Contributed by Jim Kingdon, 3-Oct-2021.)
(( E We 𝑧 ∧ ∃𝑤 𝑤𝑧) → ∃𝑥𝑧𝑦𝑧 𝑥𝑦)       (𝜑 ∨ ¬ 𝜑)

2.5.3  Transfinite induction

Theoremtfi 4305* The Principle of Transfinite Induction. Theorem 7.17 of [TakeutiZaring] p. 39. This principle states that if 𝐴 is a class of ordinal numbers with the property that every ordinal number included in 𝐴 also belongs to 𝐴, then every ordinal number is in 𝐴.

(Contributed by NM, 18-Feb-2004.)

((𝐴 ⊆ On ∧ ∀𝑥 ∈ On (𝑥𝐴𝑥𝐴)) → 𝐴 = On)

Theoremtfis 4306* Transfinite Induction Schema. If all ordinal numbers less than a given number 𝑥 have a property (induction hypothesis), then all ordinal numbers have the property (conclusion). Exercise 25 of [Enderton] p. 200. (Contributed by NM, 1-Aug-1994.) (Revised by Mario Carneiro, 20-Nov-2016.)
(𝑥 ∈ On → (∀𝑦𝑥 [𝑦 / 𝑥]𝜑𝜑))       (𝑥 ∈ On → 𝜑)

Theoremtfis2f 4307* Transfinite Induction Schema, using implicit substitution. (Contributed by NM, 18-Aug-1994.)
𝑥𝜓    &   (𝑥 = 𝑦 → (𝜑𝜓))    &   (𝑥 ∈ On → (∀𝑦𝑥 𝜓𝜑))       (𝑥 ∈ On → 𝜑)

Theoremtfis2 4308* Transfinite Induction Schema, using implicit substitution. (Contributed by NM, 18-Aug-1994.)
(𝑥 = 𝑦 → (𝜑𝜓))    &   (𝑥 ∈ On → (∀𝑦𝑥 𝜓𝜑))       (𝑥 ∈ On → 𝜑)

Theoremtfis3 4309* Transfinite Induction Schema, using implicit substitution. (Contributed by NM, 4-Nov-2003.)
(𝑥 = 𝑦 → (𝜑𝜓))    &   (𝑥 = 𝐴 → (𝜑𝜒))    &   (𝑥 ∈ On → (∀𝑦𝑥 𝜓𝜑))       (𝐴 ∈ On → 𝜒)

Theoremtfisi 4310* A transfinite induction scheme in "implicit" form where the induction is done on an object derived from the object of interest. (Contributed by Stefan O'Rear, 24-Aug-2015.)
(𝜑𝐴𝑉)    &   (𝜑𝑇 ∈ On)    &   ((𝜑 ∧ (𝑅 ∈ On ∧ 𝑅𝑇) ∧ ∀𝑦(𝑆𝑅𝜒)) → 𝜓)    &   (𝑥 = 𝑦 → (𝜓𝜒))    &   (𝑥 = 𝐴 → (𝜓𝜃))    &   (𝑥 = 𝑦𝑅 = 𝑆)    &   (𝑥 = 𝐴𝑅 = 𝑇)       (𝜑𝜃)

2.6  IZF Set Theory - add the Axiom of Infinity

2.6.1  Introduce the Axiom of Infinity

Axiomax-iinf 4311* Axiom of Infinity. Axiom 5 of [Crosilla] p. "Axioms of CZF and IZF". (Contributed by Jim Kingdon, 16-Nov-2018.)
𝑥(∅ ∈ 𝑥 ∧ ∀𝑦(𝑦𝑥 → suc 𝑦𝑥))

Theoremzfinf2 4312* A standard version of the Axiom of Infinity, using definitions to abbreviate. Axiom Inf of [BellMachover] p. 472. (Contributed by NM, 30-Aug-1993.)
𝑥(∅ ∈ 𝑥 ∧ ∀𝑦𝑥 suc 𝑦𝑥)

2.6.2  The natural numbers (i.e. finite ordinals)

Syntaxcom 4313 Extend class notation to include the class of natural numbers.
class ω

Definitiondf-iom 4314* Define the class of natural numbers as the smallest inductive set, which is valid provided we assume the Axiom of Infinity. Definition 6.3 of [Eisenberg] p. 82.

Note: the natural numbers ω are a subset of the ordinal numbers df-on 4105. Later, when we define complex numbers, we will be able to also define a subset of the complex numbers with analogous properties and operations, but they will be different sets. (Contributed by NM, 6-Aug-1994.) Use its alias dfom3 4315 instead for naming consistency with set.mm. (New usage is discouraged.)

ω = {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦𝑥 suc 𝑦𝑥)}

Theoremdfom3 4315* Alias for df-iom 4314. Use it instead of df-iom 4314 for naming consistency with set.mm. (Contributed by NM, 6-Aug-1994.)
ω = {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦𝑥 suc 𝑦𝑥)}

Theoremomex 4316 The existence of omega (the class of natural numbers). Axiom 7 of [TakeutiZaring] p. 43. (Contributed by NM, 6-Aug-1994.)
ω ∈ V

2.6.3  Peano's postulates

Theorempeano1 4317 Zero is a natural number. One of Peano's five postulates for arithmetic. Proposition 7.30(1) of [TakeutiZaring] p. 42. (Contributed by NM, 15-May-1994.)
∅ ∈ ω

Theorempeano2 4318 The successor of any natural number is a natural number. One of Peano's five postulates for arithmetic. Proposition 7.30(2) of [TakeutiZaring] p. 42. (Contributed by NM, 3-Sep-2003.)
(𝐴 ∈ ω → suc 𝐴 ∈ ω)

Theorempeano3 4319 The successor of any natural number is not zero. One of Peano's five postulates for arithmetic. Proposition 7.30(3) of [TakeutiZaring] p. 42. (Contributed by NM, 3-Sep-2003.)
(𝐴 ∈ ω → suc 𝐴 ≠ ∅)

Theorempeano4 4320 Two natural numbers are equal iff their successors are equal, i.e. the successor function is one-to-one. One of Peano's five postulates for arithmetic. Proposition 7.30(4) of [TakeutiZaring] p. 43. (Contributed by NM, 3-Sep-2003.)
((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (suc 𝐴 = suc 𝐵𝐴 = 𝐵))

Theorempeano5 4321* The induction postulate: any class containing zero and closed under the successor operation contains all natural numbers. One of Peano's five postulates for arithmetic. Proposition 7.30(5) of [TakeutiZaring] p. 43. The more traditional statement of mathematical induction as a theorem schema, with a basis and an induction step, is derived from this theorem as theorem findes 4326. (Contributed by NM, 18-Feb-2004.)
((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ 𝐴)

2.6.4  Finite induction (for finite ordinals)

Theoremfind 4322* The Principle of Finite Induction (mathematical induction). Corollary 7.31 of [TakeutiZaring] p. 43. The simpler hypothesis shown here was suggested in an email from "Colin" on 1-Oct-2001. The hypothesis states that 𝐴 is a set of natural numbers, zero belongs to 𝐴, and given any member of 𝐴 the member's successor also belongs to 𝐴. The conclusion is that every natural number is in 𝐴. (Contributed by NM, 22-Feb-2004.) (Proof shortened by Andrew Salmon, 27-Aug-2011.)
(𝐴 ⊆ ω ∧ ∅ ∈ 𝐴 ∧ ∀𝑥𝐴 suc 𝑥𝐴)       𝐴 = ω

Theoremfinds 4323* Principle of Finite Induction (inference schema), using implicit substitutions. The first four hypotheses establish the substitutions we need. The last two are the basis and the induction step. Theorem Schema 22 of [Suppes] p. 136. This is Metamath 100 proof #74. (Contributed by NM, 14-Apr-1995.)
(𝑥 = ∅ → (𝜑𝜓))    &   (𝑥 = 𝑦 → (𝜑𝜒))    &   (𝑥 = suc 𝑦 → (𝜑𝜃))    &   (𝑥 = 𝐴 → (𝜑𝜏))    &   𝜓    &   (𝑦 ∈ ω → (𝜒𝜃))       (𝐴 ∈ ω → 𝜏)

Theoremfinds2 4324* Principle of Finite Induction (inference schema), using implicit substitutions. The first three hypotheses establish the substitutions we need. The last two are the basis and the induction step. Theorem Schema 22 of [Suppes] p. 136. (Contributed by NM, 29-Nov-2002.)
(𝑥 = ∅ → (𝜑𝜓))    &   (𝑥 = 𝑦 → (𝜑𝜒))    &   (𝑥 = suc 𝑦 → (𝜑𝜃))    &   (𝜏𝜓)    &   (𝑦 ∈ ω → (𝜏 → (𝜒𝜃)))       (𝑥 ∈ ω → (𝜏𝜑))

Theoremfinds1 4325* Principle of Finite Induction (inference schema), using implicit substitutions. The first three hypotheses establish the substitutions we need. The last two are the basis and the induction step. Theorem Schema 22 of [Suppes] p. 136. (Contributed by NM, 22-Mar-2006.)
(𝑥 = ∅ → (𝜑𝜓))    &   (𝑥 = 𝑦 → (𝜑𝜒))    &   (𝑥 = suc 𝑦 → (𝜑𝜃))    &   𝜓    &   (𝑦 ∈ ω → (𝜒𝜃))       (𝑥 ∈ ω → 𝜑)

Theoremfindes 4326 Finite induction with explicit substitution. The first hypothesis is the basis and the second is the induction step. Theorem Schema 22 of [Suppes] p. 136. This is an alternative for Metamath 100 proof #74. (Contributed by Raph Levien, 9-Jul-2003.)
[∅ / 𝑥]𝜑    &   (𝑥 ∈ ω → (𝜑[suc 𝑥 / 𝑥]𝜑))       (𝑥 ∈ ω → 𝜑)

2.6.5  The Natural Numbers (continued)

Theoremnn0suc 4327* A natural number is either 0 or a successor. Similar theorems for arbitrary sets or real numbers will not be provable (without the law of the excluded middle), but equality of natural numbers is decidable. (Contributed by NM, 27-May-1998.)
(𝐴 ∈ ω → (𝐴 = ∅ ∨ ∃𝑥 ∈ ω 𝐴 = suc 𝑥))

Theoremelnn 4328 A member of a natural number is a natural number. (Contributed by NM, 21-Jun-1998.)
((𝐴𝐵𝐵 ∈ ω) → 𝐴 ∈ ω)

Theoremordom 4329 Omega is ordinal. Theorem 7.32 of [TakeutiZaring] p. 43. (Contributed by NM, 18-Oct-1995.)
Ord ω

Theoremomelon2 4330 Omega is an ordinal number. (Contributed by Mario Carneiro, 30-Jan-2013.)
(ω ∈ V → ω ∈ On)

Theoremomelon 4331 Omega is an ordinal number. (Contributed by NM, 10-May-1998.) (Revised by Mario Carneiro, 30-Jan-2013.)
ω ∈ On

Theoremnnon 4332 A natural number is an ordinal number. (Contributed by NM, 27-Jun-1994.)
(𝐴 ∈ ω → 𝐴 ∈ On)

Theoremnnoni 4333 A natural number is an ordinal number. (Contributed by NM, 27-Jun-1994.)
𝐴 ∈ ω       𝐴 ∈ On

Theoremnnord 4334 A natural number is ordinal. (Contributed by NM, 17-Oct-1995.)
(𝐴 ∈ ω → Ord 𝐴)

Theoremomsson 4335 Omega is a subset of On. (Contributed by NM, 13-Jun-1994.)
ω ⊆ On

Theoremlimom 4336 Omega is a limit ordinal. Theorem 2.8 of [BellMachover] p. 473. (Contributed by NM, 26-Mar-1995.) (Proof rewritten by Jim Kingdon, 5-Jan-2019.)
Lim ω

Theorempeano2b 4337 A class belongs to omega iff its successor does. (Contributed by NM, 3-Dec-1995.)
(𝐴 ∈ ω ↔ suc 𝐴 ∈ ω)

Theoremnnsuc 4338* A nonzero natural number is a successor. (Contributed by NM, 18-Feb-2004.)
((𝐴 ∈ ω ∧ 𝐴 ≠ ∅) → ∃𝑥 ∈ ω 𝐴 = suc 𝑥)

Theoremnndceq0 4339 A natural number is either zero or nonzero. Decidable equality for natural numbers is a special case of the law of the excluded middle which holds in most constructive set theories including ours. (Contributed by Jim Kingdon, 5-Jan-2019.)
(𝐴 ∈ ω → DECID 𝐴 = ∅)

Theorem0elnn 4340 A natural number is either the empty set or has the empty set as an element. (Contributed by Jim Kingdon, 23-Aug-2019.)
(𝐴 ∈ ω → (𝐴 = ∅ ∨ ∅ ∈ 𝐴))

Theoremnn0eln0 4341 A natural number is nonempty iff it contains the empty set. Although in constructive mathematics it is generally more natural to work with inhabited sets and ignore the whole concept of nonempty sets, in the specific case of natural numbers this theorem may be helpful in converting proofs which were written assuming excluded middle. (Contributed by Jim Kingdon, 28-Aug-2019.)
(𝐴 ∈ ω → (∅ ∈ 𝐴𝐴 ≠ ∅))

Theoremnnregexmid 4342* If inhabited sets of natural numbers always have minimal elements, excluded middle follows. The argument is essentially the same as regexmid 4260 and the larger lesson is that although natural numbers may behave "non-constructively" even in a constructive set theory (for example see nndceq 6077 or nntri3or 6072), sets of natural numbers are a different animal. (Contributed by Jim Kingdon, 6-Sep-2019.)
((𝑥 ⊆ ω ∧ ∃𝑦 𝑦𝑥) → ∃𝑦(𝑦𝑥 ∧ ∀𝑧(𝑧𝑦 → ¬ 𝑧𝑥)))       (𝜑 ∨ ¬ 𝜑)

2.6.6  Relations

Syntaxcxp 4343 Extend the definition of a class to include the cross product.
class (𝐴 × 𝐵)

Syntaxccnv 4344 Extend the definition of a class to include the converse of a class.
class 𝐴

Syntaxcdm 4345 Extend the definition of a class to include the domain of a class.
class dom 𝐴

Syntaxcrn 4346 Extend the definition of a class to include the range of a class.
class ran 𝐴

Syntaxcres 4347 Extend the definition of a class to include the restriction of a class. (Read: The restriction of 𝐴 to 𝐵.)
class (𝐴𝐵)

Syntaxcima 4348 Extend the definition of a class to include the image of a class. (Read: The image of 𝐵 under 𝐴.)
class (𝐴𝐵)

Syntaxccom 4349 Extend the definition of a class to include the composition of two classes. (Read: The composition of 𝐴 and 𝐵.)
class (𝐴𝐵)

Syntaxwrel 4350 Extend the definition of a wff to include the relation predicate. (Read: 𝐴 is a relation.)
wff Rel 𝐴

Definitiondf-xp 4351* Define the cross product of two classes. Definition 9.11 of [Quine] p. 64. For example, ( { 1 , 5 } × { 2 , 7 } ) = ( { 1 , 2 , 1 , 7 } { 5 , 2 , 5 , 7 } ) . Another example is that the set of rational numbers are defined in using the cross-product ( Z × N ) ; the left- and right-hand sides of the cross-product represent the top (integer) and bottom (natural) numbers of a fraction. (Contributed by NM, 4-Jul-1994.)
(𝐴 × 𝐵) = {⟨𝑥, 𝑦⟩ ∣ (𝑥𝐴𝑦𝐵)}

Definitiondf-rel 4352 Define the relation predicate. Definition 6.4(1) of [TakeutiZaring] p. 23. For alternate definitions, see dfrel2 4771 and dfrel3 4778. (Contributed by NM, 1-Aug-1994.)
(Rel 𝐴𝐴 ⊆ (V × V))

Definitiondf-cnv 4353* Define the converse of a class. Definition 9.12 of [Quine] p. 64. The converse of a binary relation swaps its arguments, i.e., if 𝐴 ∈ V and 𝐵 ∈ V then (𝐴𝑅𝐵𝐵𝑅𝐴), as proven in brcnv 4518 (see df-br 3765 and df-rel 4352 for more on relations). For example, { 2 , 6 , 3 , 9 } = { 6 , 2 , 9 , 3 } . We use Quine's breve accent (smile) notation. Like Quine, we use it as a prefix, which eliminates the need for parentheses. Many authors use the postfix superscript "to the minus one." "Converse" is Quine's terminology; some authors call it "inverse," especially when the argument is a function. (Contributed by NM, 4-Jul-1994.)
𝐴 = {⟨𝑥, 𝑦⟩ ∣ 𝑦𝐴𝑥}

Definitiondf-co 4354* Define the composition of two classes. Definition 6.6(3) of [TakeutiZaring] p. 24. Note that Definition 7 of [Suppes] p. 63 reverses 𝐴 and 𝐵, uses a slash instead of , and calls the operation "relative product." (Contributed by NM, 4-Jul-1994.)
(𝐴𝐵) = {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦)}

Definitiondf-dm 4355* Define the domain of a class. Definition 3 of [Suppes] p. 59. For example, F = { 2 , 6 , 3 , 9 } dom F = { 2 , 3 } . Contrast with range (defined in df-rn 4356). For alternate definitions see dfdm2 4852, dfdm3 4522, and dfdm4 4527. The notation "dom " is used by Enderton; other authors sometimes use script D. (Contributed by NM, 1-Aug-1994.)
dom 𝐴 = {𝑥 ∣ ∃𝑦 𝑥𝐴𝑦}

Definitiondf-rn 4356 Define the range of a class. For example, F = { 2 , 6 , 3 , 9 } -> ran F = { 6 , 9 } . Contrast with domain (defined in df-dm 4355). For alternate definitions, see dfrn2 4523, dfrn3 4524, and dfrn4 4781. The notation "ran " is used by Enderton; other authors sometimes use script R or script W. (Contributed by NM, 1-Aug-1994.)
ran 𝐴 = dom 𝐴

Definitiondf-res 4357 Define the restriction of a class. Definition 6.6(1) of [TakeutiZaring] p. 24. For example ( F = { 2 , 6 , 3 , 9 } B = { 1 , 2 } ) -> ( F B ) = { 2 , 6 } . (Contributed by NM, 2-Aug-1994.)
(𝐴𝐵) = (𝐴 ∩ (𝐵 × V))

Definitiondf-ima 4358 Define the image of a class (as restricted by another class). Definition 6.6(2) of [TakeutiZaring] p. 24. For example, ( F = { 2 , 6 , 3 , 9 } /\ B = { 1 , 2 } ) -> ( F B ) = { 6 } . Contrast with restriction (df-res 4357) and range (df-rn 4356). For an alternate definition, see dfima2 4670. (Contributed by NM, 2-Aug-1994.)
(𝐴𝐵) = ran (𝐴𝐵)

Theoremxpeq1 4359 Equality theorem for cross product. (Contributed by NM, 4-Jul-1994.)
(𝐴 = 𝐵 → (𝐴 × 𝐶) = (𝐵 × 𝐶))

Theoremxpeq2 4360 Equality theorem for cross product. (Contributed by NM, 5-Jul-1994.)
(𝐴 = 𝐵 → (𝐶 × 𝐴) = (𝐶 × 𝐵))

Theoremelxpi 4361* Membership in a cross product. Uses fewer axioms than elxp 4362. (Contributed by NM, 4-Jul-1994.)
(𝐴 ∈ (𝐵 × 𝐶) → ∃𝑥𝑦(𝐴 = ⟨𝑥, 𝑦⟩ ∧ (𝑥𝐵𝑦𝐶)))

Theoremelxp 4362* Membership in a cross product. (Contributed by NM, 4-Jul-1994.)
(𝐴 ∈ (𝐵 × 𝐶) ↔ ∃𝑥𝑦(𝐴 = ⟨𝑥, 𝑦⟩ ∧ (𝑥𝐵𝑦𝐶)))

Theoremelxp2 4363* Membership in a cross product. (Contributed by NM, 23-Feb-2004.)
(𝐴 ∈ (𝐵 × 𝐶) ↔ ∃𝑥𝐵𝑦𝐶 𝐴 = ⟨𝑥, 𝑦⟩)

Theoremxpeq12 4364 Equality theorem for cross product. (Contributed by FL, 31-Aug-2009.)
((𝐴 = 𝐵𝐶 = 𝐷) → (𝐴 × 𝐶) = (𝐵 × 𝐷))

Theoremxpeq1i 4365 Equality inference for cross product. (Contributed by NM, 21-Dec-2008.)
𝐴 = 𝐵       (𝐴 × 𝐶) = (𝐵 × 𝐶)

Theoremxpeq2i 4366 Equality inference for cross product. (Contributed by NM, 21-Dec-2008.)
𝐴 = 𝐵       (𝐶 × 𝐴) = (𝐶 × 𝐵)

Theoremxpeq12i 4367 Equality inference for cross product. (Contributed by FL, 31-Aug-2009.)
𝐴 = 𝐵    &   𝐶 = 𝐷       (𝐴 × 𝐶) = (𝐵 × 𝐷)

Theoremxpeq1d 4368 Equality deduction for cross product. (Contributed by Jeff Madsen, 17-Jun-2010.)
(𝜑𝐴 = 𝐵)       (𝜑 → (𝐴 × 𝐶) = (𝐵 × 𝐶))

Theoremxpeq2d 4369 Equality deduction for cross product. (Contributed by Jeff Madsen, 17-Jun-2010.)
(𝜑𝐴 = 𝐵)       (𝜑 → (𝐶 × 𝐴) = (𝐶 × 𝐵))

Theoremxpeq12d 4370 Equality deduction for cross product. (Contributed by NM, 8-Dec-2013.)
(𝜑𝐴 = 𝐵)    &   (𝜑𝐶 = 𝐷)       (𝜑 → (𝐴 × 𝐶) = (𝐵 × 𝐷))

Theoremnfxp 4371 Bound-variable hypothesis builder for cross product. (Contributed by NM, 15-Sep-2003.) (Revised by Mario Carneiro, 15-Oct-2016.)
𝑥𝐴    &   𝑥𝐵       𝑥(𝐴 × 𝐵)

Theorem0nelxp 4372 The empty set is not a member of a cross product. (Contributed by NM, 2-May-1996.) (Revised by Mario Carneiro, 26-Apr-2015.)
¬ ∅ ∈ (𝐴 × 𝐵)

Theorem0nelelxp 4373 A member of a cross product (ordered pair) doesn't contain the empty set. (Contributed by NM, 15-Dec-2008.)
(𝐶 ∈ (𝐴 × 𝐵) → ¬ ∅ ∈ 𝐶)

Theoremopelxp 4374 Ordered pair membership in a cross product. (Contributed by NM, 15-Nov-1994.) (Proof shortened by Andrew Salmon, 12-Aug-2011.) (Revised by Mario Carneiro, 26-Apr-2015.)
(⟨𝐴, 𝐵⟩ ∈ (𝐶 × 𝐷) ↔ (𝐴𝐶𝐵𝐷))

Theorembrxp 4375 Binary relation on a cross product. (Contributed by NM, 22-Apr-2004.)
(𝐴(𝐶 × 𝐷)𝐵 ↔ (𝐴𝐶𝐵𝐷))

Theoremopelxpi 4376 Ordered pair membership in a cross product (implication). (Contributed by NM, 28-May-1995.)
((𝐴𝐶𝐵𝐷) → ⟨𝐴, 𝐵⟩ ∈ (𝐶 × 𝐷))

Theoremopelxp1 4377 The first member of an ordered pair of classes in a cross product belongs to first cross product argument. (Contributed by NM, 28-May-2008.) (Revised by Mario Carneiro, 26-Apr-2015.)
(⟨𝐴, 𝐵⟩ ∈ (𝐶 × 𝐷) → 𝐴𝐶)

Theoremopelxp2 4378 The second member of an ordered pair of classes in a cross product belongs to second cross product argument. (Contributed by Mario Carneiro, 26-Apr-2015.)
(⟨𝐴, 𝐵⟩ ∈ (𝐶 × 𝐷) → 𝐵𝐷)

Theoremotelxp1 4379 The first member of an ordered triple of classes in a cross product belongs to first cross product argument. (Contributed by NM, 28-May-2008.)
(⟨⟨𝐴, 𝐵⟩, 𝐶⟩ ∈ ((𝑅 × 𝑆) × 𝑇) → 𝐴𝑅)

Theoremrabxp 4380* Membership in a class builder restricted to a cross product. (Contributed by NM, 20-Feb-2014.)
(𝑥 = ⟨𝑦, 𝑧⟩ → (𝜑𝜓))       {𝑥 ∈ (𝐴 × 𝐵) ∣ 𝜑} = {⟨𝑦, 𝑧⟩ ∣ (𝑦𝐴𝑧𝐵𝜓)}

Theorembrrelex12 4381 A true binary relation on a relation implies the arguments are sets. (This is a property of our ordered pair definition.) (Contributed by Mario Carneiro, 26-Apr-2015.)
((Rel 𝑅𝐴𝑅𝐵) → (𝐴 ∈ V ∧ 𝐵 ∈ V))

Theorembrrelex 4382 A true binary relation on a relation implies the first argument is a set. (This is a property of our ordered pair definition.) (Contributed by NM, 18-May-2004.) (Revised by Mario Carneiro, 26-Apr-2015.)
((Rel 𝑅𝐴𝑅𝐵) → 𝐴 ∈ V)

Theorembrrelex2 4383 A true binary relation on a relation implies the second argument is a set. (This is a property of our ordered pair definition.) (Contributed by Mario Carneiro, 26-Apr-2015.)
((Rel 𝑅𝐴𝑅𝐵) → 𝐵 ∈ V)

Theorembrrelexi 4384 The first argument of a binary relation exists. (An artifact of our ordered pair definition.) (Contributed by NM, 4-Jun-1998.)
Rel 𝑅       (𝐴𝑅𝐵𝐴 ∈ V)

Theorembrrelex2i 4385 The second argument of a binary relation exists. (An artifact of our ordered pair definition.) (Contributed by Mario Carneiro, 26-Apr-2015.)
Rel 𝑅       (𝐴𝑅𝐵𝐵 ∈ V)

Theoremnprrel 4386 No proper class is related to anything via any relation. (Contributed by Roy F. Longton, 30-Jul-2005.)
Rel 𝑅    &    ¬ 𝐴 ∈ V        ¬ 𝐴𝑅𝐵

Theoremfconstmpt 4387* Representation of a constant function using the mapping operation. (Note that 𝑥 cannot appear free in 𝐵.) (Contributed by NM, 12-Oct-1999.) (Revised by Mario Carneiro, 16-Nov-2013.)
(𝐴 × {𝐵}) = (𝑥𝐴𝐵)

Theoremvtoclr 4388* Variable to class conversion of transitive relation. (Contributed by NM, 9-Jun-1998.) (Revised by Mario Carneiro, 26-Apr-2015.)
Rel 𝑅    &   ((𝑥𝑅𝑦𝑦𝑅𝑧) → 𝑥𝑅𝑧)       ((𝐴𝑅𝐵𝐵𝑅𝐶) → 𝐴𝑅𝐶)

Theoremopelvvg 4389 Ordered pair membership in the universal class of ordered pairs. (Contributed by Mario Carneiro, 3-May-2015.)
((𝐴𝑉𝐵𝑊) → ⟨𝐴, 𝐵⟩ ∈ (V × V))

Theoremopelvv 4390 Ordered pair membership in the universal class of ordered pairs. (Contributed by NM, 22-Aug-2013.) (Revised by Mario Carneiro, 26-Apr-2015.)
𝐴 ∈ V    &   𝐵 ∈ V       𝐴, 𝐵⟩ ∈ (V × V)

Theoremopthprc 4391 Justification theorem for an ordered pair definition that works for any classes, including proper classes. This is a possible definition implied by the footnote in [Jech] p. 78, which says, "The sophisticated reader will not object to our use of a pair of classes." (Contributed by NM, 28-Sep-2003.)
(((𝐴 × {∅}) ∪ (𝐵 × {{∅}})) = ((𝐶 × {∅}) ∪ (𝐷 × {{∅}})) ↔ (𝐴 = 𝐶𝐵 = 𝐷))

Theorembrel 4392 Two things in a binary relation belong to the relation's domain. (Contributed by NM, 17-May-1996.) (Revised by Mario Carneiro, 26-Apr-2015.)
𝑅 ⊆ (𝐶 × 𝐷)       (𝐴𝑅𝐵 → (𝐴𝐶𝐵𝐷))

Theorembrab2a 4393* Ordered pair membership in an ordered pair class abstraction. (Contributed by Mario Carneiro, 9-Nov-2015.)
((𝑥 = 𝐴𝑦 = 𝐵) → (𝜑𝜓))    &   𝑅 = {⟨𝑥, 𝑦⟩ ∣ ((𝑥𝐶𝑦𝐷) ∧ 𝜑)}       (𝐴𝑅𝐵 ↔ ((𝐴𝐶𝐵𝐷) ∧ 𝜓))

Theoremelxp3 4394* Membership in a cross product. (Contributed by NM, 5-Mar-1995.)
(𝐴 ∈ (𝐵 × 𝐶) ↔ ∃𝑥𝑦(⟨𝑥, 𝑦⟩ = 𝐴 ∧ ⟨𝑥, 𝑦⟩ ∈ (𝐵 × 𝐶)))

Theoremopeliunxp 4395 Membership in a union of cross products. (Contributed by Mario Carneiro, 29-Dec-2014.) (Revised by Mario Carneiro, 1-Jan-2017.)
(⟨𝑥, 𝐶⟩ ∈ 𝑥𝐴 ({𝑥} × 𝐵) ↔ (𝑥𝐴𝐶𝐵))

Theoremxpundi 4396 Distributive law for cross product over union. Theorem 103 of [Suppes] p. 52. (Contributed by NM, 12-Aug-2004.)
(𝐴 × (𝐵𝐶)) = ((𝐴 × 𝐵) ∪ (𝐴 × 𝐶))

Theoremxpundir 4397 Distributive law for cross product over union. Similar to Theorem 103 of [Suppes] p. 52. (Contributed by NM, 30-Sep-2002.)
((𝐴𝐵) × 𝐶) = ((𝐴 × 𝐶) ∪ (𝐵 × 𝐶))

Theoremxpiundi 4398* Distributive law for cross product over indexed union. (Contributed by Mario Carneiro, 27-Apr-2014.)
(𝐶 × 𝑥𝐴 𝐵) = 𝑥𝐴 (𝐶 × 𝐵)

Theoremxpiundir 4399* Distributive law for cross product over indexed union. (Contributed by Mario Carneiro, 27-Apr-2014.)
( 𝑥𝐴 𝐵 × 𝐶) = 𝑥𝐴 (𝐵 × 𝐶)

Theoremiunxpconst 4400* Membership in a union of cross products when the second factor is constant. (Contributed by Mario Carneiro, 29-Dec-2014.)
𝑥𝐴 ({𝑥} × 𝐵) = (𝐴 × 𝐵)

Page List
Jump to page: Contents  1 1-100 2 101-200 3 201-300 4 301-400 5 401-500 6 501-600 7 601-700 8 701-800 9 801-900 10 901-1000 11 1001-1100 12 1101-1200 13 1201-1300 14 1301-1400 15 1401-1500 16 1501-1600 17 1601-1700 18 1701-1800 19 1801-1900 20 1901-2000 21 2001-2100 22 2101-2200 23 2201-2300 24 2301-2400 25 2401-2500 26 2501-2600 27 2601-2700 28 2701-2800 29 2801-2900 30 2901-3000 31 3001-3100 32 3101-3200 33 3201-3300 34 3301-3400 35 3401-3500 36 3501-3600 37 3601-3700 38 3701-3800 39 3801-3900 40 3901-4000 41 4001-4100 42 4101-4200 43 4201-4300 44 4301-4400 45 4401-4500 46 4501-4600 47 4601-4700 48 4701-4800 49 4801-4900 50 4901-5000 51 5001-5100 52 5101-5200 53 5201-5300 54 5301-5400 55 5401-5500 56 5501-5600 57 5601-5700 58 5701-5800 59 5801-5900 60 5901-6000 61 6001-6100 62 6101-6200 63 6201-6300 64 6301-6400 65 6401-6500 66 6501-6600 67 6601-6700 68 6701-6800 69 6801-6900 70 6901-7000 71 7001-7100 72 7101-7200 73 7201-7300 74 7301-7400 75 7401-7500 76 7501-7600 77 7601-7700 78 7701-7800 79 7801-7900 80 7901-8000 81 8001-8100 82 8101-8200 83 8201-8300 84 8301-8400 85 8401-8500 86 8501-8600 87 8601-8700 88 8701-8800 89 8801-8900 90 8901-9000 91 9001-9100 92 9101-9200 93 9201-9300 94 9301-9400 95 9401-9500 96 9501-9600 97 9601-9700 98 9701-9800 99 9801-9900 100 9901-10000 101 10001-10100 102 10101-10124
 Copyright terms: Public domain < Previous  Next >