![]() |
Metamath
Proof Explorer Theorem List (p. 66 of 480) | < Previous Next > |
Bad symbols? Try the
GIF version. |
||
Mirrors > Metamath Home Page > MPE Home Page > Theorem List Contents > Recent Proofs This page: Page List |
Color key: | ![]() (1-30438) |
![]() (30439-31961) |
![]() (31962-47939) |
Type | Label | Description |
---|---|---|
Statement | ||
Theorem | cbviotaw 6501* | Change bound variables in a description binder. Version of cbviota 6504 with a disjoint variable condition, which does not require ax-13 2369. (Contributed by Andrew Salmon, 1-Aug-2011.) Avoid ax-13 2369. (Revised by Gino Giotto, 26-Jan-2024.) |
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) & ⊢ Ⅎ𝑦𝜑 & ⊢ Ⅎ𝑥𝜓 ⇒ ⊢ (℩𝑥𝜑) = (℩𝑦𝜓) | ||
Theorem | cbviotavw 6502* | Change bound variables in a description binder. Version of cbviotav 6505 with a disjoint variable condition, which requires fewer axioms . (Contributed by Andrew Salmon, 1-Aug-2011.) (Revised by Gino Giotto, 30-Sep-2024.) |
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) ⇒ ⊢ (℩𝑥𝜑) = (℩𝑦𝜓) | ||
Theorem | cbviotavwOLD 6503* | Obsolete version of cbviotavw 6502 as of 30-Sep-2024. (Contributed by Andrew Salmon, 1-Aug-2011.) (Revised by Gino Giotto, 26-Jan-2024.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) ⇒ ⊢ (℩𝑥𝜑) = (℩𝑦𝜓) | ||
Theorem | cbviota 6504 | Change bound variables in a description binder. Usage of this theorem is discouraged because it depends on ax-13 2369. Use the weaker cbviotaw 6501 when possible. (Contributed by Andrew Salmon, 1-Aug-2011.) (New usage is discouraged.) |
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) & ⊢ Ⅎ𝑦𝜑 & ⊢ Ⅎ𝑥𝜓 ⇒ ⊢ (℩𝑥𝜑) = (℩𝑦𝜓) | ||
Theorem | cbviotav 6505* | Change bound variables in a description binder. Usage of this theorem is discouraged because it depends on ax-13 2369. Use the weaker cbviotavw 6502 when possible. (Contributed by Andrew Salmon, 1-Aug-2011.) (New usage is discouraged.) |
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) ⇒ ⊢ (℩𝑥𝜑) = (℩𝑦𝜓) | ||
Theorem | sb8iota 6506 | Variable substitution in description binder. Compare sb8eu 2592. Usage of this theorem is discouraged because it depends on ax-13 2369. (Contributed by NM, 18-Mar-2013.) (New usage is discouraged.) |
⊢ Ⅎ𝑦𝜑 ⇒ ⊢ (℩𝑥𝜑) = (℩𝑦[𝑦 / 𝑥]𝜑) | ||
Theorem | iotaeq 6507 | Equality theorem for descriptions. Usage of this theorem is discouraged because it depends on ax-13 2369. (Contributed by Andrew Salmon, 30-Jun-2011.) (New usage is discouraged.) |
⊢ (∀𝑥 𝑥 = 𝑦 → (℩𝑥𝜑) = (℩𝑦𝜑)) | ||
Theorem | iotabi 6508 | Equivalence theorem for descriptions. (Contributed by Andrew Salmon, 30-Jun-2011.) |
⊢ (∀𝑥(𝜑 ↔ 𝜓) → (℩𝑥𝜑) = (℩𝑥𝜓)) | ||
Theorem | uniabio 6509* | Part of Theorem 8.17 in [Quine] p. 56. This theorem serves as a lemma for the fundamental property of iota. (Contributed by Andrew Salmon, 11-Jul-2011.) |
⊢ (∀𝑥(𝜑 ↔ 𝑥 = 𝑦) → ∪ {𝑥 ∣ 𝜑} = 𝑦) | ||
Theorem | iotaval2 6510* | Version of iotaval 6513 using df-iota 6494 instead of dfiota2 6495. (Contributed by SN, 6-Nov-2024.) |
⊢ ({𝑥 ∣ 𝜑} = {𝑦} → (℩𝑥𝜑) = 𝑦) | ||
Theorem | iotauni2 6511* | Version of iotauni 6517 using df-iota 6494 instead of dfiota2 6495. (Contributed by SN, 6-Nov-2024.) |
⊢ (∃𝑦{𝑥 ∣ 𝜑} = {𝑦} → (℩𝑥𝜑) = ∪ {𝑥 ∣ 𝜑}) | ||
Theorem | iotanul2 6512* | Version of iotanul 6520 using df-iota 6494 instead of dfiota2 6495. (Contributed by SN, 6-Nov-2024.) |
⊢ (¬ ∃𝑦{𝑥 ∣ 𝜑} = {𝑦} → (℩𝑥𝜑) = ∅) | ||
Theorem | iotaval 6513* | Theorem 8.19 in [Quine] p. 57. This theorem is the fundamental property of iota. (Contributed by Andrew Salmon, 11-Jul-2011.) Remove dependency on ax-10 2135, ax-11 2152, ax-12 2169. (Revised by SN, 23-Nov-2024.) |
⊢ (∀𝑥(𝜑 ↔ 𝑥 = 𝑦) → (℩𝑥𝜑) = 𝑦) | ||
Theorem | iotassuni 6514 | The ℩ class is a subset of the union of all elements satisfying 𝜑. (Contributed by Mario Carneiro, 24-Dec-2016.) Remove dependency on ax-10 2135, ax-11 2152, ax-12 2169. (Revised by SN, 6-Nov-2024.) |
⊢ (℩𝑥𝜑) ⊆ ∪ {𝑥 ∣ 𝜑} | ||
Theorem | iotaex 6515 | Theorem 8.23 in [Quine] p. 58. This theorem proves the existence of the ℩ class under our definition. (Contributed by Andrew Salmon, 11-Jul-2011.) Remove dependency on ax-10 2135, ax-11 2152, ax-12 2169. (Revised by SN, 6-Nov-2024.) |
⊢ (℩𝑥𝜑) ∈ V | ||
Theorem | iotavalOLD 6516* | Obsolete version of iotaval 6513 as of 23-Dec-2024. (Contributed by Andrew Salmon, 11-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (∀𝑥(𝜑 ↔ 𝑥 = 𝑦) → (℩𝑥𝜑) = 𝑦) | ||
Theorem | iotauni 6517 | Equivalence between two different forms of ℩. (Contributed by Andrew Salmon, 12-Jul-2011.) |
⊢ (∃!𝑥𝜑 → (℩𝑥𝜑) = ∪ {𝑥 ∣ 𝜑}) | ||
Theorem | iotaint 6518 | Equivalence between two different forms of ℩. (Contributed by Mario Carneiro, 24-Dec-2016.) |
⊢ (∃!𝑥𝜑 → (℩𝑥𝜑) = ∩ {𝑥 ∣ 𝜑}) | ||
Theorem | iota1 6519 | Property of iota. (Contributed by NM, 23-Aug-2011.) (Revised by Mario Carneiro, 23-Dec-2016.) |
⊢ (∃!𝑥𝜑 → (𝜑 ↔ (℩𝑥𝜑) = 𝑥)) | ||
Theorem | iotanul 6520 | Theorem 8.22 in [Quine] p. 57. This theorem is the result if there isn't exactly one 𝑥 that satisfies 𝜑. (Contributed by Andrew Salmon, 11-Jul-2011.) |
⊢ (¬ ∃!𝑥𝜑 → (℩𝑥𝜑) = ∅) | ||
Theorem | iotassuniOLD 6521 | Obsolete version of iotassuni 6514 as of 23-Dec-2024. (Contributed by Mario Carneiro, 24-Dec-2016.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (℩𝑥𝜑) ⊆ ∪ {𝑥 ∣ 𝜑} | ||
Theorem | iotaexOLD 6522 | Obsolete version of iotaex 6515 as of 23-Dec-2024. (Contributed by Andrew Salmon, 11-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (℩𝑥𝜑) ∈ V | ||
Theorem | iota4 6523 | Theorem *14.22 in [WhiteheadRussell] p. 190. (Contributed by Andrew Salmon, 12-Jul-2011.) |
⊢ (∃!𝑥𝜑 → [(℩𝑥𝜑) / 𝑥]𝜑) | ||
Theorem | iota4an 6524 | Theorem *14.23 in [WhiteheadRussell] p. 191. (Contributed by Andrew Salmon, 12-Jul-2011.) |
⊢ (∃!𝑥(𝜑 ∧ 𝜓) → [(℩𝑥(𝜑 ∧ 𝜓)) / 𝑥]𝜑) | ||
Theorem | iota5 6525* | A method for computing iota. (Contributed by NM, 17-Sep-2013.) |
⊢ ((𝜑 ∧ 𝐴 ∈ 𝑉) → (𝜓 ↔ 𝑥 = 𝐴)) ⇒ ⊢ ((𝜑 ∧ 𝐴 ∈ 𝑉) → (℩𝑥𝜓) = 𝐴) | ||
Theorem | iotabidv 6526* | Formula-building deduction for iota. (Contributed by NM, 20-Aug-2011.) |
⊢ (𝜑 → (𝜓 ↔ 𝜒)) ⇒ ⊢ (𝜑 → (℩𝑥𝜓) = (℩𝑥𝜒)) | ||
Theorem | iotabii 6527 | Formula-building deduction for iota. (Contributed by Mario Carneiro, 2-Oct-2015.) |
⊢ (𝜑 ↔ 𝜓) ⇒ ⊢ (℩𝑥𝜑) = (℩𝑥𝜓) | ||
Theorem | iotacl 6528 |
Membership law for descriptions.
This can be useful for expanding an unbounded iota-based definition (see df-iota 6494). If you have a bounded iota-based definition, riotacl2 7384 may be useful. (Contributed by Andrew Salmon, 1-Aug-2011.) |
⊢ (∃!𝑥𝜑 → (℩𝑥𝜑) ∈ {𝑥 ∣ 𝜑}) | ||
Theorem | iota2df 6529 | A condition that allows to represent "the unique element such that 𝜑 " with a class expression 𝐴. (Contributed by NM, 30-Dec-2014.) |
⊢ (𝜑 → 𝐵 ∈ 𝑉) & ⊢ (𝜑 → ∃!𝑥𝜓) & ⊢ ((𝜑 ∧ 𝑥 = 𝐵) → (𝜓 ↔ 𝜒)) & ⊢ Ⅎ𝑥𝜑 & ⊢ (𝜑 → Ⅎ𝑥𝜒) & ⊢ (𝜑 → Ⅎ𝑥𝐵) ⇒ ⊢ (𝜑 → (𝜒 ↔ (℩𝑥𝜓) = 𝐵)) | ||
Theorem | iota2d 6530* | A condition that allows to represent "the unique element such that 𝜑 " with a class expression 𝐴. (Contributed by NM, 30-Dec-2014.) |
⊢ (𝜑 → 𝐵 ∈ 𝑉) & ⊢ (𝜑 → ∃!𝑥𝜓) & ⊢ ((𝜑 ∧ 𝑥 = 𝐵) → (𝜓 ↔ 𝜒)) ⇒ ⊢ (𝜑 → (𝜒 ↔ (℩𝑥𝜓) = 𝐵)) | ||
Theorem | iota2 6531* | The unique element such that 𝜑. (Contributed by Jeff Madsen, 1-Jun-2011.) (Revised by Mario Carneiro, 23-Dec-2016.) |
⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ⇒ ⊢ ((𝐴 ∈ 𝐵 ∧ ∃!𝑥𝜑) → (𝜓 ↔ (℩𝑥𝜑) = 𝐴)) | ||
Theorem | iotan0 6532* | Representation of "the unique element such that 𝜑 " with a class expression 𝐴 which is not the empty set (that means that "the unique element such that 𝜑 " exists). (Contributed by AV, 30-Jan-2024.) |
⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐴 ≠ ∅ ∧ 𝐴 = (℩𝑥𝜑)) → 𝜓) | ||
Theorem | sniota 6533 | A class abstraction with a unique member can be expressed as a singleton. (Contributed by Mario Carneiro, 23-Dec-2016.) |
⊢ (∃!𝑥𝜑 → {𝑥 ∣ 𝜑} = {(℩𝑥𝜑)}) | ||
Theorem | dfiota4 6534 | The ℩ operation using the if operator. (Contributed by Scott Fenton, 6-Oct-2017.) (Proof shortened by JJ, 28-Oct-2021.) |
⊢ (℩𝑥𝜑) = if(∃!𝑥𝜑, ∪ {𝑥 ∣ 𝜑}, ∅) | ||
Theorem | csbiota 6535* | Class substitution within a description binder. (Contributed by Scott Fenton, 6-Oct-2017.) (Revised by NM, 23-Aug-2018.) |
⊢ ⦋𝐴 / 𝑥⦌(℩𝑦𝜑) = (℩𝑦[𝐴 / 𝑥]𝜑) | ||
Syntax | wfun 6536 | Extend the definition of a wff to include the function predicate. (Read: 𝐴 is a function.) |
wff Fun 𝐴 | ||
Syntax | wfn 6537 | Extend the definition of a wff to include the function predicate with a domain. (Read: 𝐴 is a function on 𝐵.) |
wff 𝐴 Fn 𝐵 | ||
Syntax | wf 6538 | Extend the definition of a wff to include the function predicate with domain and codomain. (Read: 𝐹 maps 𝐴 into 𝐵.) |
wff 𝐹:𝐴⟶𝐵 | ||
Syntax | wf1 6539 | Extend the definition of a wff to include one-to-one functions. (Read: 𝐹 maps 𝐴 one-to-one into 𝐵.) The notation ("1-1" above the arrow) is from Definition 6.15(5) of [TakeutiZaring] p. 27. |
wff 𝐹:𝐴–1-1→𝐵 | ||
Syntax | wfo 6540 | Extend the definition of a wff to include onto functions. (Read: 𝐹 maps 𝐴 onto 𝐵.) The notation ("onto" below the arrow) is from Definition 6.15(4) of [TakeutiZaring] p. 27. |
wff 𝐹:𝐴–onto→𝐵 | ||
Syntax | wf1o 6541 | Extend the definition of a wff to include one-to-one onto functions. (Read: 𝐹 maps 𝐴 one-to-one onto 𝐵.) The notation ("1-1" above the arrow and "onto" below the arrow) is from Definition 6.15(6) of [TakeutiZaring] p. 27. |
wff 𝐹:𝐴–1-1-onto→𝐵 | ||
Syntax | cfv 6542 | Extend the definition of a class to include the value of a function. Read: "the value of 𝐹 at 𝐴", or "𝐹 of 𝐴". |
class (𝐹‘𝐴) | ||
Syntax | wiso 6543 | Extend the definition of a wff to include the isomorphism property. Read: "𝐻 is an 𝑅, 𝑆 isomorphism of 𝐴 onto 𝐵". |
wff 𝐻 Isom 𝑅, 𝑆 (𝐴, 𝐵) | ||
Definition | df-fun 6544 | Define predicate that determines if some class 𝐴 is a function. Definition 10.1 of [Quine] p. 65. For example, the expression Fun cos is true once we define cosine (df-cos 16018). This is not the same as defining a specific function's mapping, which is typically done using the format of cmpt 5230 with the maps-to notation (see df-mpt 5231 and df-mpo 7416). Contrast this predicate with the predicates to determine if some class is a function with a given domain (df-fn 6545), a function with a given domain and codomain (df-f 6546), a one-to-one function (df-f1 6547), an onto function (df-fo 6548), or a one-to-one onto function (df-f1o 6549). For alternate definitions, see dffun2 6552, dffun3 6556, dffun4 6558, dffun5 6559, dffun6 6555, dffun7 6574, dffun8 6575, and dffun9 6576. (Contributed by NM, 1-Aug-1994.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ (𝐴 ∘ ◡𝐴) ⊆ I )) | ||
Definition | df-fn 6545 | Define a function with domain. Definition 6.15(1) of [TakeutiZaring] p. 27. For alternate definitions, see dffn2 6718, dffn3 6729, dffn4 6810, and dffn5 6949. (Contributed by NM, 1-Aug-1994.) |
⊢ (𝐴 Fn 𝐵 ↔ (Fun 𝐴 ∧ dom 𝐴 = 𝐵)) | ||
Definition | df-f 6546 | Define a function (mapping) with domain and codomain. Definition 6.15(3) of [TakeutiZaring] p. 27. 𝐹:𝐴⟶𝐵 can be read as "𝐹 is a function from 𝐴 to 𝐵". For alternate definitions, see dff2 7099, dff3 7100, and dff4 7101. (Contributed by NM, 1-Aug-1994.) |
⊢ (𝐹:𝐴⟶𝐵 ↔ (𝐹 Fn 𝐴 ∧ ran 𝐹 ⊆ 𝐵)) | ||
Definition | df-f1 6547 |
Define a one-to-one function. For equivalent definitions see dff12 6785
and dff13 7256. Compare Definition 6.15(5) of [TakeutiZaring] p. 27. We
use their notation ("1-1" above the arrow).
A one-to-one function is also called an "injection" or an "injective function", 𝐹:𝐴–1-1→𝐵 can be read as "𝐹 is an injection from 𝐴 into 𝐵". Injections are precisely the monomorphisms in the category SetCat of sets and set functions, see setcmon 18041. (Contributed by NM, 1-Aug-1994.) |
⊢ (𝐹:𝐴–1-1→𝐵 ↔ (𝐹:𝐴⟶𝐵 ∧ Fun ◡𝐹)) | ||
Definition | df-fo 6548 |
Define an onto function. Definition 6.15(4) of [TakeutiZaring] p. 27.
We use their notation ("onto" under the arrow). For alternate
definitions, see dffo2 6808, dffo3 7102, dffo4 7103, and dffo5 7104.
An onto function is also called a "surjection" or a "surjective function", 𝐹:𝐴–onto→𝐵 can be read as "𝐹 is a surjection from 𝐴 onto 𝐵". Surjections are precisely the epimorphisms in the category SetCat of sets and set functions, see setcepi 18042. (Contributed by NM, 1-Aug-1994.) |
⊢ (𝐹:𝐴–onto→𝐵 ↔ (𝐹 Fn 𝐴 ∧ ran 𝐹 = 𝐵)) | ||
Definition | df-f1o 6549 |
Define a one-to-one onto function. For equivalent definitions see
dff1o2 6837, dff1o3 6838, dff1o4 6840, and dff1o5 6841. Compare Definition
6.15(6) of [TakeutiZaring] p. 27.
We use their notation ("1-1" above
the arrow and "onto" below the arrow).
A one-to-one onto function is also called a "bijection" or a "bijective function", 𝐹:𝐴–1-1-onto→𝐵 can be read as "𝐹 is a bijection between 𝐴 and 𝐵". Bijections are precisely the isomorphisms in the category SetCat of sets and set functions, see setciso 18045. Therefore, two sets are called "isomorphic" if there is a bijection between them. According to isof1oidb 7323, two sets are isomorphic iff there is an isomorphism Isom regarding the identity relation. In this case, the two sets are also "equinumerous", see bren 8951. (Contributed by NM, 1-Aug-1994.) |
⊢ (𝐹:𝐴–1-1-onto→𝐵 ↔ (𝐹:𝐴–1-1→𝐵 ∧ 𝐹:𝐴–onto→𝐵)) | ||
Definition | df-fv 6550* | Define the value of a function, (𝐹‘𝐴), also known as function application. For example, (cos‘0) = 1 (we prove this in cos0 16097 after we define cosine in df-cos 16018). Typically, function 𝐹 is defined using maps-to notation (see df-mpt 5231 and df-mpo 7416), but this is not required. For example, 𝐹 = {⟨2, 6⟩, ⟨3, 9⟩} → (𝐹‘3) = 9 (ex-fv 29963). Note that df-ov 7414 will define two-argument functions using ordered pairs as (𝐴𝐹𝐵) = (𝐹‘⟨𝐴, 𝐵⟩). This particular definition is quite convenient: it can be applied to any class and evaluates to the empty set when it is not meaningful (as shown by ndmfv 6925 and fvprc 6882). The left apostrophe notation originated with Peano and was adopted in Definition *30.01 of [WhiteheadRussell] p. 235, Definition 10.11 of [Quine] p. 68, and Definition 6.11 of [TakeutiZaring] p. 26. It means the same thing as the more familiar 𝐹(𝐴) notation for a function's value at 𝐴, i.e., "𝐹 of 𝐴", but without context-dependent notational ambiguity. Alternate definitions are dffv2 6985, dffv3 6886, fv2 6885, and fv3 6908 (the latter two previously required 𝐴 to be a set.) Restricted equivalents that require 𝐹 to be a function are shown in funfv 6977 and funfv2 6978. For the familiar definition of function value in terms of ordered pair membership, see funopfvb 6946. (Contributed by NM, 1-Aug-1994.) Revised to use ℩. Original version is now Theorem dffv4 6887. (Revised by Scott Fenton, 6-Oct-2017.) |
⊢ (𝐹‘𝐴) = (℩𝑥𝐴𝐹𝑥) | ||
Definition | df-isom 6551* | Define the isomorphism predicate. We read this as "𝐻 is an 𝑅, 𝑆 isomorphism of 𝐴 onto 𝐵". Normally, 𝑅 and 𝑆 are ordering relations on 𝐴 and 𝐵 respectively. Definition 6.28 of [TakeutiZaring] p. 32, whose notation is the same as ours except that 𝑅 and 𝑆 are subscripts. (Contributed by NM, 4-Mar-1997.) |
⊢ (𝐻 Isom 𝑅, 𝑆 (𝐴, 𝐵) ↔ (𝐻:𝐴–1-1-onto→𝐵 ∧ ∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 (𝑥𝑅𝑦 ↔ (𝐻‘𝑥)𝑆(𝐻‘𝑦)))) | ||
Theorem | dffun2 6552* | Alternate definition of a function. (Contributed by NM, 29-Dec-1996.) Avoid ax-10 2135, ax-12 2169. (Revised by SN, 19-Dec-2024.) Avoid ax-11 2152. (Revised by BTernaryTau, 29-Dec-2024.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑥𝐴𝑧) → 𝑦 = 𝑧))) | ||
Theorem | dffun2OLD 6553* | Obsolete version of dffun2 6552 as of 29-Dec-2024. (Contributed by NM, 29-Dec-1996.) Avoid ax-10 2135, ax-12 2169. (Revised by SN, 19-Dec-2024.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑥𝐴𝑧) → 𝑦 = 𝑧))) | ||
Theorem | dffun2OLDOLD 6554* | Obsolete version of dffun2 6552 as of 11-Dec-2024. (Contributed by NM, 29-Dec-1996.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑥𝐴𝑧) → 𝑦 = 𝑧))) | ||
Theorem | dffun6 6555* | Alternate definition of a function using "at most one" notation. (Contributed by NM, 9-Mar-1995.) Avoid ax-10 2135, ax-12 2169. (Revised by SN, 19-Dec-2024.) |
⊢ (Fun 𝐹 ↔ (Rel 𝐹 ∧ ∀𝑥∃*𝑦 𝑥𝐹𝑦)) | ||
Theorem | dffun3 6556* | Alternate definition of function. (Contributed by NM, 29-Dec-1996.) (Proof shortened by SN, 19-Dec-2024.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∃𝑧∀𝑦(𝑥𝐴𝑦 → 𝑦 = 𝑧))) | ||
Theorem | dffun3OLD 6557* | Obsolete version of dffun3 6556 as of 19-Dec-2024. Alternate definition of function. (Contributed by NM, 29-Dec-1996.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∃𝑧∀𝑦(𝑥𝐴𝑦 → 𝑦 = 𝑧))) | ||
Theorem | dffun4 6558* | Alternate definition of a function. Definition 6.4(4) of [TakeutiZaring] p. 24. (Contributed by NM, 29-Dec-1996.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∀𝑦∀𝑧((⟨𝑥, 𝑦⟩ ∈ 𝐴 ∧ ⟨𝑥, 𝑧⟩ ∈ 𝐴) → 𝑦 = 𝑧))) | ||
Theorem | dffun5 6559* | Alternate definition of function. (Contributed by NM, 29-Dec-1996.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∃𝑧∀𝑦(⟨𝑥, 𝑦⟩ ∈ 𝐴 → 𝑦 = 𝑧))) | ||
Theorem | dffun6f 6560* | Definition of function, using bound-variable hypotheses instead of distinct variable conditions. (Contributed by NM, 9-Mar-1995.) (Revised by Mario Carneiro, 15-Oct-2016.) |
⊢ Ⅎ𝑥𝐴 & ⊢ Ⅎ𝑦𝐴 ⇒ ⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥∃*𝑦 𝑥𝐴𝑦)) | ||
Theorem | dffun6OLD 6561* | Obsolete version of dffun6 6555 as of 19-Dec-2024. (Contributed by NM, 9-Mar-1995.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (Fun 𝐹 ↔ (Rel 𝐹 ∧ ∀𝑥∃*𝑦 𝑥𝐹𝑦)) | ||
Theorem | funmo 6562* | A function has at most one value for each argument. (Contributed by NM, 24-May-1998.) (Proof shortened by SN, 19-Dec-2024.) |
⊢ (Fun 𝐹 → ∃*𝑦 𝐴𝐹𝑦) | ||
Theorem | funmoOLD 6563* | Obsolete version of funmo 6562 as of 19-Dec-2024. (Contributed by NM, 24-May-1998.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (Fun 𝐹 → ∃*𝑦 𝐴𝐹𝑦) | ||
Theorem | funrel 6564 | A function is a relation. (Contributed by NM, 1-Aug-1994.) |
⊢ (Fun 𝐴 → Rel 𝐴) | ||
Theorem | 0nelfun 6565 | A function does not contain the empty set. (Contributed by BJ, 26-Nov-2021.) |
⊢ (Fun 𝑅 → ∅ ∉ 𝑅) | ||
Theorem | funss 6566 | Subclass theorem for function predicate. (Contributed by NM, 16-Aug-1994.) (Proof shortened by Mario Carneiro, 24-Jun-2014.) |
⊢ (𝐴 ⊆ 𝐵 → (Fun 𝐵 → Fun 𝐴)) | ||
Theorem | funeq 6567 | Equality theorem for function predicate. (Contributed by NM, 16-Aug-1994.) |
⊢ (𝐴 = 𝐵 → (Fun 𝐴 ↔ Fun 𝐵)) | ||
Theorem | funeqi 6568 | Equality inference for the function predicate. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.) |
⊢ 𝐴 = 𝐵 ⇒ ⊢ (Fun 𝐴 ↔ Fun 𝐵) | ||
Theorem | funeqd 6569 | Equality deduction for the function predicate. (Contributed by NM, 23-Feb-2013.) |
⊢ (𝜑 → 𝐴 = 𝐵) ⇒ ⊢ (𝜑 → (Fun 𝐴 ↔ Fun 𝐵)) | ||
Theorem | nffun 6570 | Bound-variable hypothesis builder for a function. (Contributed by NM, 30-Jan-2004.) |
⊢ Ⅎ𝑥𝐹 ⇒ ⊢ Ⅎ𝑥Fun 𝐹 | ||
Theorem | sbcfung 6571 | Distribute proper substitution through the function predicate. (Contributed by Alexander van der Vekens, 23-Jul-2017.) |
⊢ (𝐴 ∈ 𝑉 → ([𝐴 / 𝑥]Fun 𝐹 ↔ Fun ⦋𝐴 / 𝑥⦌𝐹)) | ||
Theorem | funeu 6572* | There is exactly one value of a function. (Contributed by NM, 22-Apr-2004.) (Proof shortened by Andrew Salmon, 17-Sep-2011.) |
⊢ ((Fun 𝐹 ∧ 𝐴𝐹𝐵) → ∃!𝑦 𝐴𝐹𝑦) | ||
Theorem | funeu2 6573* | There is exactly one value of a function. (Contributed by NM, 3-Aug-1994.) |
⊢ ((Fun 𝐹 ∧ ⟨𝐴, 𝐵⟩ ∈ 𝐹) → ∃!𝑦⟨𝐴, 𝑦⟩ ∈ 𝐹) | ||
Theorem | dffun7 6574* | Alternate definition of a function. One possibility for the definition of a function in [Enderton] p. 42. (Enderton's definition is ambiguous because "there is only one" could mean either "there is at most one" or "there is exactly one". However, dffun8 6575 shows that it does not matter which meaning we pick.) (Contributed by NM, 4-Nov-2002.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥 ∈ dom 𝐴∃*𝑦 𝑥𝐴𝑦)) | ||
Theorem | dffun8 6575* | Alternate definition of a function. One possibility for the definition of a function in [Enderton] p. 42. Compare dffun7 6574. (Contributed by NM, 4-Nov-2002.) (Proof shortened by Andrew Salmon, 17-Sep-2011.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥 ∈ dom 𝐴∃!𝑦 𝑥𝐴𝑦)) | ||
Theorem | dffun9 6576* | Alternate definition of a function. (Contributed by NM, 28-Mar-2007.) (Revised by NM, 16-Jun-2017.) |
⊢ (Fun 𝐴 ↔ (Rel 𝐴 ∧ ∀𝑥 ∈ dom 𝐴∃*𝑦 ∈ ran 𝐴 𝑥𝐴𝑦)) | ||
Theorem | funfn 6577 | A class is a function if and only if it is a function on its domain. (Contributed by NM, 13-Aug-2004.) |
⊢ (Fun 𝐴 ↔ 𝐴 Fn dom 𝐴) | ||
Theorem | funfnd 6578 | A function is a function on its domain. (Contributed by Glauco Siliprandi, 23-Oct-2021.) |
⊢ (𝜑 → Fun 𝐴) ⇒ ⊢ (𝜑 → 𝐴 Fn dom 𝐴) | ||
Theorem | funi 6579 | The identity relation is a function. Part of Theorem 10.4 of [Quine] p. 65. See also idfn 6677. (Contributed by NM, 30-Apr-1998.) |
⊢ Fun I | ||
Theorem | nfunv 6580 | The universal class is not a function. (Contributed by Raph Levien, 27-Jan-2004.) |
⊢ ¬ Fun V | ||
Theorem | funopg 6581 | A Kuratowski ordered pair of sets is a function only if its components are equal. (Contributed by NM, 5-Jun-2008.) (Revised by Mario Carneiro, 26-Apr-2015.) A function is a class of ordered pairs, so the fact that an ordered pair may sometimes be itself a function is an "accident" depending on the specific encoding of ordered pairs as classes (in set.mm, the Kuratowski encoding). A more meaningful statement is funsng 6598, as relsnopg 5802 is to relop 5849. (New usage is discouraged.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ Fun ⟨𝐴, 𝐵⟩) → 𝐴 = 𝐵) | ||
Theorem | funopab 6582* | A class of ordered pairs is a function when there is at most one second member for each pair. (Contributed by NM, 16-May-1995.) |
⊢ (Fun {⟨𝑥, 𝑦⟩ ∣ 𝜑} ↔ ∀𝑥∃*𝑦𝜑) | ||
Theorem | funopabeq 6583* | A class of ordered pairs of values is a function. (Contributed by NM, 14-Nov-1995.) |
⊢ Fun {⟨𝑥, 𝑦⟩ ∣ 𝑦 = 𝐴} | ||
Theorem | funopab4 6584* | A class of ordered pairs of values in the form used by df-mpt 5231 is a function. (Contributed by NM, 17-Feb-2013.) |
⊢ Fun {⟨𝑥, 𝑦⟩ ∣ (𝜑 ∧ 𝑦 = 𝐴)} | ||
Theorem | funmpt 6585 | A function in maps-to notation is a function. (Contributed by Mario Carneiro, 13-Jan-2013.) |
⊢ Fun (𝑥 ∈ 𝐴 ↦ 𝐵) | ||
Theorem | funmpt2 6586 | Functionality of a class given by a maps-to notation. (Contributed by FL, 17-Feb-2008.) (Revised by Mario Carneiro, 31-May-2014.) |
⊢ 𝐹 = (𝑥 ∈ 𝐴 ↦ 𝐵) ⇒ ⊢ Fun 𝐹 | ||
Theorem | funco 6587 | The composition of two functions is a function. Exercise 29 of [TakeutiZaring] p. 25. (Contributed by NM, 26-Jan-1997.) (Proof shortened by Andrew Salmon, 17-Sep-2011.) |
⊢ ((Fun 𝐹 ∧ Fun 𝐺) → Fun (𝐹 ∘ 𝐺)) | ||
Theorem | funresfunco 6588 | Composition of two functions, generalization of funco 6587. (Contributed by Alexander van der Vekens, 25-Jul-2017.) |
⊢ ((Fun (𝐹 ↾ ran 𝐺) ∧ Fun 𝐺) → Fun (𝐹 ∘ 𝐺)) | ||
Theorem | funres 6589 | A restriction of a function is a function. Compare Exercise 18 of [TakeutiZaring] p. 25. (Contributed by NM, 16-Aug-1994.) |
⊢ (Fun 𝐹 → Fun (𝐹 ↾ 𝐴)) | ||
Theorem | funresd 6590 | A restriction of a function is a function. (Contributed by Glauco Siliprandi, 2-Jan-2022.) |
⊢ (𝜑 → Fun 𝐹) ⇒ ⊢ (𝜑 → Fun (𝐹 ↾ 𝐴)) | ||
Theorem | funssres 6591 | The restriction of a function to the domain of a subclass equals the subclass. (Contributed by NM, 15-Aug-1994.) |
⊢ ((Fun 𝐹 ∧ 𝐺 ⊆ 𝐹) → (𝐹 ↾ dom 𝐺) = 𝐺) | ||
Theorem | fun2ssres 6592 | Equality of restrictions of a function and a subclass. (Contributed by NM, 16-Aug-1994.) |
⊢ ((Fun 𝐹 ∧ 𝐺 ⊆ 𝐹 ∧ 𝐴 ⊆ dom 𝐺) → (𝐹 ↾ 𝐴) = (𝐺 ↾ 𝐴)) | ||
Theorem | funun 6593 | The union of functions with disjoint domains is a function. Theorem 4.6 of [Monk1] p. 43. (Contributed by NM, 12-Aug-1994.) |
⊢ (((Fun 𝐹 ∧ Fun 𝐺) ∧ (dom 𝐹 ∩ dom 𝐺) = ∅) → Fun (𝐹 ∪ 𝐺)) | ||
Theorem | fununmo 6594* | If the union of classes is a function, there is at most one element in relation to an arbitrary element regarding one of these classes. (Contributed by AV, 18-Jul-2019.) |
⊢ (Fun (𝐹 ∪ 𝐺) → ∃*𝑦 𝑥𝐹𝑦) | ||
Theorem | fununfun 6595 | If the union of classes is a function, the classes itselves are functions. (Contributed by AV, 18-Jul-2019.) |
⊢ (Fun (𝐹 ∪ 𝐺) → (Fun 𝐹 ∧ Fun 𝐺)) | ||
Theorem | fundif 6596 | A function with removed elements is still a function. (Contributed by AV, 7-Jun-2021.) |
⊢ (Fun 𝐹 → Fun (𝐹 ∖ 𝐴)) | ||
Theorem | funcnvsn 6597 | The converse singleton of an ordered pair is a function. This is equivalent to funsn 6600 via cnvsn 6224, but stating it this way allows to skip the sethood assumptions on 𝐴 and 𝐵. (Contributed by NM, 30-Apr-2015.) |
⊢ Fun ◡{⟨𝐴, 𝐵⟩} | ||
Theorem | funsng 6598 | A singleton of an ordered pair is a function. Theorem 10.5 of [Quine] p. 65. (Contributed by NM, 28-Jun-2011.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → Fun {⟨𝐴, 𝐵⟩}) | ||
Theorem | fnsng 6599 | Functionality and domain of the singleton of an ordered pair. (Contributed by Mario Carneiro, 30-Apr-2015.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → {⟨𝐴, 𝐵⟩} Fn {𝐴}) | ||
Theorem | funsn 6600 | A singleton of an ordered pair is a function. Theorem 10.5 of [Quine] p. 65. (Contributed by NM, 12-Aug-1994.) |
⊢ 𝐴 ∈ V & ⊢ 𝐵 ∈ V ⇒ ⊢ Fun {⟨𝐴, 𝐵⟩} |
< Previous Next > |
Copyright terms: Public domain | < Previous Next > |