P. 151 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 15001-15100   *Has distinct variable group(s)

Type	Label	Description
Statement
Theorem	clsslem 15001*	The closure of a subclass is a subclass of the closure. (Contributed by RP, 16-May-2020.)
⊢ (𝑅 ⊆ 𝑆 → ∩ {𝑟 ∣ (𝑅 ⊆ 𝑟 ∧ 𝜑)} ⊆ ∩ {𝑟 ∣ (𝑆 ⊆ 𝑟 ∧ 𝜑)})
5.8.3  Definitions and basic properties of transitive closures
Syntax	ctcl 15002	Extend class notation to include the transitive closure symbol.
class t+
Syntax	crtcl 15003	Extend class notation with reflexive-transitive closure.
class t*
Definition	df-trcl 15004*	Transitive closure of a relation. This is the smallest superset which has the transitive property. (Contributed by FL, 27-Jun-2011.)
⊢ t+ = (𝑥 ∈ V ↦ ∩ {𝑧 ∣ (𝑥 ⊆ 𝑧 ∧ (𝑧 ∘ 𝑧) ⊆ 𝑧)})
Definition	df-rtrcl 15005*	Reflexive-transitive closure of a relation. This is the smallest superset which is reflexive property over all elements of its domain and range and has the transitive property. (Contributed by FL, 27-Jun-2011.)
⊢ t* = (𝑥 ∈ V ↦ ∩ {𝑧 ∣ (( I ↾ (dom 𝑥 ∪ ran 𝑥)) ⊆ 𝑧 ∧ 𝑥 ⊆ 𝑧 ∧ (𝑧 ∘ 𝑧) ⊆ 𝑧)})
Theorem	trcleq1 15006*	Equality of relations implies equality of transitive closures. (Contributed by RP, 9-May-2020.)
⊢ (𝑅 = 𝑆 → ∩ {𝑟 ∣ (𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟)} = ∩ {𝑟 ∣ (𝑆 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟)})
Theorem	trclsslem 15007*	The transitive closure (as a relation) of a subclass is a subclass of the transitive closure. (Contributed by RP, 3-May-2020.)
⊢ (𝑅 ⊆ 𝑆 → ∩ {𝑟 ∣ (𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟)} ⊆ ∩ {𝑟 ∣ (𝑆 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟)})
Theorem	trcleq2lem 15008	Equality implies bijection. (Contributed by RP, 5-May-2020.)
⊢ (𝐴 = 𝐵 → ((𝑅 ⊆ 𝐴 ∧ (𝐴 ∘ 𝐴) ⊆ 𝐴) ↔ (𝑅 ⊆ 𝐵 ∧ (𝐵 ∘ 𝐵) ⊆ 𝐵)))
Theorem	cvbtrcl 15009*	Change of bound variable in class of all transitive relations which are supersets of a relation. (Contributed by RP, 5-May-2020.)
⊢ {𝑥 ∣ (𝑅 ⊆ 𝑥 ∧ (𝑥 ∘ 𝑥) ⊆ 𝑥)} = {𝑦 ∣ (𝑅 ⊆ 𝑦 ∧ (𝑦 ∘ 𝑦) ⊆ 𝑦)}
Theorem	trcleq12lem 15010	Equality implies bijection. (Contributed by RP, 9-May-2020.)
⊢ ((𝑅 = 𝑆 ∧ 𝐴 = 𝐵) → ((𝑅 ⊆ 𝐴 ∧ (𝐴 ∘ 𝐴) ⊆ 𝐴) ↔ (𝑆 ⊆ 𝐵 ∧ (𝐵 ∘ 𝐵) ⊆ 𝐵)))
Theorem	trclexlem 15011	Existence of relation implies existence of union with Cartesian product of domain and range. (Contributed by RP, 5-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝑅 ∪ (dom 𝑅 × ran 𝑅)) ∈ V)
Theorem	trclublem 15012*	If a relation exists then the class of transitive relations which are supersets of that relation is not empty. (Contributed by RP, 28-Apr-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝑅 ∪ (dom 𝑅 × ran 𝑅)) ∈ {𝑥 ∣ (𝑅 ⊆ 𝑥 ∧ (𝑥 ∘ 𝑥) ⊆ 𝑥)})
Theorem	trclubi 15013*	The Cartesian product of the domain and range of a relation is an upper bound for its transitive closure. (Contributed by RP, 2-Jan-2020.) (Revised by RP, 28-Apr-2020.) (Revised by AV, 26-Mar-2021.)
⊢ Rel 𝑅    &   ⊢ 𝑅 ∈ V    ⇒   ⊢ ∩ {𝑠 ∣ (𝑅 ⊆ 𝑠 ∧ (𝑠 ∘ 𝑠) ⊆ 𝑠)} ⊆ (dom 𝑅 × ran 𝑅)
Theorem	trclubgi 15014*	The union with the Cartesian product of its domain and range is an upper bound for a set's transitive closure. (Contributed by RP, 3-Jan-2020.) (Revised by RP, 28-Apr-2020.) (Revised by AV, 26-Mar-2021.)
⊢ 𝑅 ∈ V    ⇒   ⊢ ∩ {𝑠 ∣ (𝑅 ⊆ 𝑠 ∧ (𝑠 ∘ 𝑠) ⊆ 𝑠)} ⊆ (𝑅 ∪ (dom 𝑅 × ran 𝑅))
Theorem	trclub 15015*	The Cartesian product of the domain and range of a relation is an upper bound for its transitive closure. (Contributed by RP, 17-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ Rel 𝑅) → ∩ {𝑟 ∣ (𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟)} ⊆ (dom 𝑅 × ran 𝑅))
Theorem	trclubg 15016*	The union with the Cartesian product of its domain and range is an upper bound for a set's transitive closure (as a relation). (Contributed by RP, 17-May-2020.)
⊢ (𝑅 ∈ 𝑉 → ∩ {𝑟 ∣ (𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟)} ⊆ (𝑅 ∪ (dom 𝑅 × ran 𝑅)))
Theorem	trclfv 15017*	The transitive closure of a relation. (Contributed by RP, 28-Apr-2020.)
⊢ (𝑅 ∈ 𝑉 → (t+‘𝑅) = ∩ {𝑥 ∣ (𝑅 ⊆ 𝑥 ∧ (𝑥 ∘ 𝑥) ⊆ 𝑥)})
Theorem	brintclab 15018*	Two ways to express a binary relation which is the intersection of a class. (Contributed by RP, 4-Apr-2020.)
⊢ (𝐴∩ {𝑥 ∣ 𝜑}𝐵 ↔ ∀𝑥(𝜑 → ⟨𝐴, 𝐵⟩ ∈ 𝑥))
Theorem	brtrclfv 15019*	Two ways of expressing the transitive closure of a binary relation. (Contributed by RP, 9-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝐴(t+‘𝑅)𝐵 ↔ ∀𝑟((𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟) → 𝐴𝑟𝐵)))
Theorem	brcnvtrclfv 15020*	Two ways of expressing the transitive closure of the converse of a binary relation. (Contributed by RP, 9-May-2020.)
⊢ ((𝑅 ∈ 𝑈 ∧ 𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (𝐴◡(t+‘𝑅)𝐵 ↔ ∀𝑟((𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟) → 𝐵𝑟𝐴)))
Theorem	brtrclfvcnv 15021*	Two ways of expressing the transitive closure of the converse of a binary relation. (Contributed by RP, 10-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝐴(t+‘◡𝑅)𝐵 ↔ ∀𝑟((◡𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟) → 𝐴𝑟𝐵)))
Theorem	brcnvtrclfvcnv 15022*	Two ways of expressing the transitive closure of the converse of the converse of a binary relation. (Contributed by RP, 10-May-2020.)
⊢ ((𝑅 ∈ 𝑈 ∧ 𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (𝐴◡(t+‘◡𝑅)𝐵 ↔ ∀𝑟((◡𝑅 ⊆ 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟) → 𝐵𝑟𝐴)))
Theorem	trclfvss 15023	The transitive closure (as a relation) of a subclass is a subclass of the transitive closure. (Contributed by RP, 3-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ 𝑆 ∈ 𝑊 ∧ 𝑅 ⊆ 𝑆) → (t+‘𝑅) ⊆ (t+‘𝑆))
Theorem	trclfvub 15024	The transitive closure of a relation has an upper bound. (Contributed by RP, 28-Apr-2020.)
⊢ (𝑅 ∈ 𝑉 → (t+‘𝑅) ⊆ (𝑅 ∪ (dom 𝑅 × ran 𝑅)))
Theorem	trclfvlb 15025	The transitive closure of a relation has a lower bound. (Contributed by RP, 28-Apr-2020.)
⊢ (𝑅 ∈ 𝑉 → 𝑅 ⊆ (t+‘𝑅))
Theorem	trclfvcotr 15026	The transitive closure of a relation is a transitive relation. (Contributed by RP, 29-Apr-2020.)
⊢ (𝑅 ∈ 𝑉 → ((t+‘𝑅) ∘ (t+‘𝑅)) ⊆ (t+‘𝑅))
Theorem	trclfvlb2 15027	The transitive closure of a relation has a lower bound. (Contributed by RP, 8-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝑅 ∘ 𝑅) ⊆ (t+‘𝑅))
Theorem	trclfvlb3 15028	The transitive closure of a relation has a lower bound. (Contributed by RP, 8-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝑅 ∪ (𝑅 ∘ 𝑅)) ⊆ (t+‘𝑅))
Theorem	cotrtrclfv 15029	The transitive closure of a transitive relation. (Contributed by RP, 28-Apr-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ (𝑅 ∘ 𝑅) ⊆ 𝑅) → (t+‘𝑅) = 𝑅)
Theorem	trclidm 15030	The transitive closure of a relation is idempotent. (Contributed by RP, 29-Apr-2020.)
⊢ (𝑅 ∈ 𝑉 → (t+‘(t+‘𝑅)) = (t+‘𝑅))
Theorem	trclun 15031	Transitive closure of a union of relations. (Contributed by RP, 5-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ 𝑆 ∈ 𝑊) → (t+‘(𝑅 ∪ 𝑆)) = (t+‘((t+‘𝑅) ∪ (t+‘𝑆))))
Theorem	trclfvg 15032	The value of the transitive closure of a relation is a superset or (for proper classes) the empty set. (Contributed by RP, 8-May-2020.)
⊢ (𝑅 ⊆ (t+‘𝑅) ∨ (t+‘𝑅) = ∅)
Theorem	trclfvcotrg 15033	The value of the transitive closure of a relation is always a transitive relation. (Contributed by RP, 8-May-2020.)
⊢ ((t+‘𝑅) ∘ (t+‘𝑅)) ⊆ (t+‘𝑅)
Theorem	reltrclfv 15034	The transitive closure of a relation is a relation. (Contributed by RP, 9-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ Rel 𝑅) → Rel (t+‘𝑅))
Theorem	dmtrclfv 15035	The domain of the transitive closure is equal to the domain of the relation. (Contributed by RP, 9-May-2020.)
⊢ (𝑅 ∈ 𝑉 → dom (t+‘𝑅) = dom 𝑅)
5.8.4  Exponentiation of relations
Syntax	crelexp 15036	Extend class notation to include relation exponentiation.
class ↑𝑟
Definition	df-relexp 15037*	Definition of repeated composition of a relation with itself, aka relation exponentiation. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 22-May-2020.)
⊢ ↑𝑟 = (𝑟 ∈ V, 𝑛 ∈ ℕ0 ↦ if(𝑛 = 0, ( I ↾ (dom 𝑟 ∪ ran 𝑟)), (seq1((𝑥 ∈ V, 𝑦 ∈ V ↦ (𝑥 ∘ 𝑟)), (𝑧 ∈ V ↦ 𝑟))‘𝑛)))
Theorem	reldmrelexp 15038	The domain of the repeated composition of a relation is a relation. (Contributed by AV, 12-Jul-2024.)
⊢ Rel dom ↑𝑟
Theorem	relexp0g 15039	A relation composed zero times is the (restricted) identity. (Contributed by RP, 22-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝑅↑𝑟0) = ( I ↾ (dom 𝑅 ∪ ran 𝑅)))
Theorem	relexp0 15040	A relation composed zero times is the (restricted) identity. (Contributed by RP, 22-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ Rel 𝑅) → (𝑅↑𝑟0) = ( I ↾ ∪ ∪ 𝑅))
Theorem	relexp0d 15041	A relation composed zero times is the (restricted) identity. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    &   ⊢ (𝜑 → 𝑅 ∈ 𝑉)    ⇒   ⊢ (𝜑 → (𝑅↑𝑟0) = ( I ↾ ∪ ∪ 𝑅))
Theorem	relexpsucnnr 15042	A reduction for relation exponentiation to the right. (Contributed by RP, 22-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑅↑𝑟(𝑁 + 1)) = ((𝑅↑𝑟𝑁) ∘ 𝑅))
Theorem	relexp1g 15043	A relation composed once is itself. (Contributed by RP, 22-May-2020.)
⊢ (𝑅 ∈ 𝑉 → (𝑅↑𝑟1) = 𝑅)
Theorem	dfid5 15044	Identity relation is equal to relational exponentiation to the first power. (Contributed by RP, 9-Jun-2020.)
⊢ I = (𝑥 ∈ V ↦ (𝑥↑𝑟1))
Theorem	dfid6 15045*	Identity relation expressed as indexed union of relational powers. (Contributed by RP, 9-Jun-2020.)
⊢ I = (𝑥 ∈ V ↦ ∪ 𝑛 ∈ {1} (𝑥↑𝑟𝑛))
Theorem	relexp1d 15046	A relation composed once is itself. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → 𝑅 ∈ 𝑉)    ⇒   ⊢ (𝜑 → (𝑅↑𝑟1) = 𝑅)
Theorem	relexpsucnnl 15047	A reduction for relation exponentiation to the left. (Contributed by RP, 23-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ 𝑁 ∈ ℕ) → (𝑅↑𝑟(𝑁 + 1)) = (𝑅 ∘ (𝑅↑𝑟𝑁)))
Theorem	relexpsucl 15048	A reduction for relation exponentiation to the left. (Contributed by RP, 23-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ Rel 𝑅 ∧ 𝑁 ∈ ℕ0) → (𝑅↑𝑟(𝑁 + 1)) = (𝑅 ∘ (𝑅↑𝑟𝑁)))
Theorem	relexpsucr 15049	A reduction for relation exponentiation to the right. (Contributed by RP, 23-May-2020.)
⊢ ((𝑅 ∈ 𝑉 ∧ Rel 𝑅 ∧ 𝑁 ∈ ℕ0) → (𝑅↑𝑟(𝑁 + 1)) = ((𝑅↑𝑟𝑁) ∘ 𝑅))
Theorem	relexpsucrd 15050	A reduction for relation exponentiation to the right. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → (𝑅↑𝑟(𝑁 + 1)) = ((𝑅↑𝑟𝑁) ∘ 𝑅))
Theorem	relexpsucld 15051	A reduction for relation exponentiation to the left. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → (𝑅↑𝑟(𝑁 + 1)) = (𝑅 ∘ (𝑅↑𝑟𝑁)))
Theorem	relexpcnv 15052	Commutation of converse and relation exponentiation. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉) → ◡(𝑅↑𝑟𝑁) = (◡𝑅↑𝑟𝑁))
Theorem	relexpcnvd 15053	Commutation of converse and relation exponentiation. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → 𝑅 ∈ 𝑉)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → ◡(𝑅↑𝑟𝑁) = (◡𝑅↑𝑟𝑁))
Theorem	relexp0rel 15054	The exponentiation of a class to zero is a relation. (Contributed by RP, 23-May-2020.)
⊢ (𝑅 ∈ 𝑉 → Rel (𝑅↑𝑟0))
Theorem	relexprelg 15055	The exponentiation of a class is a relation except when the exponent is one and the class is not a relation. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉 ∧ (𝑁 = 1 → Rel 𝑅)) → Rel (𝑅↑𝑟𝑁))
Theorem	relexprel 15056	The exponentiation of a relation is a relation. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉 ∧ Rel 𝑅) → Rel (𝑅↑𝑟𝑁))
Theorem	relexpreld 15057	The exponentiation of a relation is a relation. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → Rel (𝑅↑𝑟𝑁))
Theorem	relexpnndm 15058	The domain of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ ∧ 𝑅 ∈ 𝑉) → dom (𝑅↑𝑟𝑁) ⊆ dom 𝑅)
Theorem	relexpdmg 15059	The domain of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉) → dom (𝑅↑𝑟𝑁) ⊆ (dom 𝑅 ∪ ran 𝑅))
Theorem	relexpdm 15060	The domain of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉) → dom (𝑅↑𝑟𝑁) ⊆ ∪ ∪ 𝑅)
Theorem	relexpdmd 15061	The domain of an exponentiation of a relation a subset of the relation's field. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → dom (𝑅↑𝑟𝑁) ⊆ ∪ ∪ 𝑅)
Theorem	relexpnnrn 15062	The range of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ ∧ 𝑅 ∈ 𝑉) → ran (𝑅↑𝑟𝑁) ⊆ ran 𝑅)
Theorem	relexprng 15063	The range of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉) → ran (𝑅↑𝑟𝑁) ⊆ (dom 𝑅 ∪ ran 𝑅))
Theorem	relexprn 15064	The range of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉) → ran (𝑅↑𝑟𝑁) ⊆ ∪ ∪ 𝑅)
Theorem	relexprnd 15065	The range of an exponentiation of a relation a subset of the relation's field. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → ran (𝑅↑𝑟𝑁) ⊆ ∪ ∪ 𝑅)
Theorem	relexpfld 15066	The field of an exponentiation of a relation a subset of the relation's field. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉) → ∪ ∪ (𝑅↑𝑟𝑁) ⊆ ∪ ∪ 𝑅)
Theorem	relexpfldd 15067	The field of an exponentiation of a relation a subset of the relation's field. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → 𝑁 ∈ ℕ0)    ⇒   ⊢ (𝜑 → ∪ ∪ (𝑅↑𝑟𝑁) ⊆ ∪ ∪ 𝑅)
Theorem	relexpaddnn 15068	Relation composition becomes addition under exponentiation. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ ℕ ∧ 𝑀 ∈ ℕ ∧ 𝑅 ∈ 𝑉) → ((𝑅↑𝑟𝑁) ∘ (𝑅↑𝑟𝑀)) = (𝑅↑𝑟(𝑁 + 𝑀)))
Theorem	relexpuzrel 15069	The exponentiation of a class to an integer not smaller than 2 is a relation. (Contributed by RP, 23-May-2020.)
⊢ ((𝑁 ∈ (ℤ≥‘2) ∧ 𝑅 ∈ 𝑉) → Rel (𝑅↑𝑟𝑁))
Theorem	relexpaddg 15070	Relation composition becomes addition under exponentiation except when the exponents total to one and the class isn't a relation. (Contributed by RP, 30-May-2020.)
⊢ ((𝑁 ∈ ℕ0 ∧ (𝑀 ∈ ℕ0 ∧ 𝑅 ∈ 𝑉 ∧ ((𝑁 + 𝑀) = 1 → Rel 𝑅))) → ((𝑅↑𝑟𝑁) ∘ (𝑅↑𝑟𝑀)) = (𝑅↑𝑟(𝑁 + 𝑀)))
Theorem	relexpaddd 15071	Relation composition becomes addition under exponentiation. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ0)    &   ⊢ (𝜑 → 𝑀 ∈ ℕ0)    ⇒   ⊢ (𝜑 → ((𝑅↑𝑟𝑁) ∘ (𝑅↑𝑟𝑀)) = (𝑅↑𝑟(𝑁 + 𝑀)))
5.8.5  Reflexive-transitive closure as an indexed union
Syntax	crtrcl 15072	Extend class notation with recursively defined reflexive, transitive closure.
class t*rec
Definition	df-rtrclrec 15073*	The reflexive, transitive closure of a relation constructed as the union of all finite exponentiations. (Contributed by Drahflow, 12-Nov-2015.)
⊢ t*rec = (𝑟 ∈ V ↦ ∪ 𝑛 ∈ ℕ0 (𝑟↑𝑟𝑛))
Theorem	rtrclreclem1 15074	The reflexive, transitive closure is indeed a closure. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 12-Jul-2024.)
⊢ (𝜑 → 𝑅 ∈ 𝑉)    ⇒   ⊢ (𝜑 → 𝑅 ⊆ (t*rec‘𝑅))
Theorem	dfrtrclrec2 15075*	If two elements are connected by a reflexive, transitive closure, then they are connected via 𝑛 instances the relation, for some 𝑛. (Contributed by Drahflow, 12-Nov-2015.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    ⇒   ⊢ (𝜑 → (𝐴(t*rec‘𝑅)𝐵 ↔ ∃𝑛 ∈ ℕ0 𝐴(𝑅↑𝑟𝑛)𝐵))
Theorem	rtrclreclem2 15076	The reflexive, transitive closure is indeed reflexive. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    &   ⊢ (𝜑 → 𝑅 ∈ 𝑉)    ⇒   ⊢ (𝜑 → ( I ↾ ∪ ∪ 𝑅) ⊆ (t*rec‘𝑅))
Theorem	rtrclreclem3 15077	The reflexive, transitive closure is indeed transitive. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    ⇒   ⊢ (𝜑 → ((t*rec‘𝑅) ∘ (t*rec‘𝑅)) ⊆ (t*rec‘𝑅))
Theorem	rtrclreclem4 15078*	The reflexive, transitive closure of 𝑅 is the smallest reflexive, transitive relation which contains 𝑅 and the identity. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    ⇒   ⊢ (𝜑 → ∀𝑠((( I ↾ (dom 𝑅 ∪ ran 𝑅)) ⊆ 𝑠 ∧ 𝑅 ⊆ 𝑠 ∧ (𝑠 ∘ 𝑠) ⊆ 𝑠) → (t*rec‘𝑅) ⊆ 𝑠))
Theorem	dfrtrcl2 15079	The two definitions t* and t*rec of the reflexive, transitive closure coincide if 𝑅 is indeed a relation. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜑 → Rel 𝑅)    ⇒   ⊢ (𝜑 → (t*‘𝑅) = (t*rec‘𝑅))
5.8.6  Principle of transitive induction. If we have a statement that holds for some element, and a relation between elements that implies if it holds for the first element then it must hold for the second element, the principle of transitive induction shows the statement holds for any element related to the first by the (reflexive-)transitive closure of the relation.
Theorem	relexpindlem 15080*	Principle of transitive induction, finite and non-class version. The first three hypotheses give various existences, the next three give necessary substitutions and the last two are the basis and the induction hypothesis. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Proof shortened by Peter Mazsa, 2-Oct-2022.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜂 → Rel 𝑅)    &   ⊢ (𝜂 → 𝑆 ∈ 𝑉)    &   ⊢ (𝑖 = 𝑆 → (𝜑 ↔ 𝜒))    &   ⊢ (𝑖 = 𝑥 → (𝜑 ↔ 𝜓))    &   ⊢ (𝑖 = 𝑗 → (𝜑 ↔ 𝜃))    &   ⊢ (𝜂 → 𝜒)    &   ⊢ (𝜂 → (𝑗𝑅𝑥 → (𝜃 → 𝜓)))    ⇒   ⊢ (𝜂 → (𝑛 ∈ ℕ0 → (𝑆(𝑅↑𝑟𝑛)𝑥 → 𝜓)))
Theorem	relexpind 15081*	Principle of transitive induction, finite version. The first three hypotheses give various existences, the next four give necessary substitutions and the last two are the basis and the induction hypothesis. (Contributed by Drahflow, 12-Nov-2015.) (Revised by RP, 30-May-2020.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜂 → Rel 𝑅)    &   ⊢ (𝜂 → 𝑆 ∈ 𝑉)    &   ⊢ (𝜂 → 𝑋 ∈ 𝑊)    &   ⊢ (𝑖 = 𝑆 → (𝜑 ↔ 𝜒))    &   ⊢ (𝑖 = 𝑥 → (𝜑 ↔ 𝜓))    &   ⊢ (𝑖 = 𝑗 → (𝜑 ↔ 𝜃))    &   ⊢ (𝑥 = 𝑋 → (𝜓 ↔ 𝜏))    &   ⊢ (𝜂 → 𝜒)    &   ⊢ (𝜂 → (𝑗𝑅𝑥 → (𝜃 → 𝜓)))    ⇒   ⊢ (𝜂 → (𝑛 ∈ ℕ0 → (𝑆(𝑅↑𝑟𝑛)𝑋 → 𝜏)))
Theorem	rtrclind 15082*	Principle of transitive induction. The first three hypotheses give various existences, the next four give necessary substitutions and the last two are the basis and the induction step. (Contributed by Drahflow, 12-Nov-2015.) (Revised by AV, 13-Jul-2024.)
⊢ (𝜂 → Rel 𝑅)    &   ⊢ (𝜂 → 𝑆 ∈ 𝑉)    &   ⊢ (𝜂 → 𝑋 ∈ 𝑊)    &   ⊢ (𝑖 = 𝑆 → (𝜑 ↔ 𝜒))    &   ⊢ (𝑖 = 𝑥 → (𝜑 ↔ 𝜓))    &   ⊢ (𝑖 = 𝑗 → (𝜑 ↔ 𝜃))    &   ⊢ (𝑥 = 𝑋 → (𝜓 ↔ 𝜏))    &   ⊢ (𝜂 → 𝜒)    &   ⊢ (𝜂 → (𝑗𝑅𝑥 → (𝜃 → 𝜓)))    ⇒   ⊢ (𝜂 → (𝑆(t*‘𝑅)𝑋 → 𝜏))
5.9  Elementary real and complex functions
5.9.1  The "shift" operation
Syntax	cshi 15083	Extend class notation with function shifter.
class shift
Definition	df-shft 15084*	Define a function shifter. This operation offsets the value argument of a function (ordinarily on a subset of ℂ) and produces a new function on ℂ. See shftval 15091 for its value. (Contributed by NM, 20-Jul-2005.)
⊢ shift = (𝑓 ∈ V, 𝑥 ∈ ℂ ↦ {⟨𝑦, 𝑧⟩ ∣ (𝑦 ∈ ℂ ∧ (𝑦 − 𝑥)𝑓𝑧)})
Theorem	shftlem 15085*	Two ways to write a shifted set (𝐵 + 𝐴). (Contributed by Mario Carneiro, 3-Nov-2013.)
⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ⊆ ℂ) → {𝑥 ∈ ℂ ∣ (𝑥 − 𝐴) ∈ 𝐵} = {𝑥 ∣ ∃𝑦 ∈ 𝐵 𝑥 = (𝑦 + 𝐴)})
Theorem	shftuz 15086*	A shift of the upper integers. (Contributed by Mario Carneiro, 5-Nov-2013.)
⊢ ((𝐴 ∈ ℤ ∧ 𝐵 ∈ ℤ) → {𝑥 ∈ ℂ ∣ (𝑥 − 𝐴) ∈ (ℤ≥‘𝐵)} = (ℤ≥‘(𝐵 + 𝐴)))
Theorem	shftfval 15087*	The value of the sequence shifter operation is a function on ℂ. 𝐴 is ordinarily an integer. (Contributed by NM, 20-Jul-2005.) (Revised by Mario Carneiro, 3-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ (𝐴 ∈ ℂ → (𝐹 shift 𝐴) = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ℂ ∧ (𝑥 − 𝐴)𝐹𝑦)})
Theorem	shftdm 15088*	Domain of a relation shifted by 𝐴. The set on the right is more commonly notated as (dom 𝐹 + 𝐴) (meaning add 𝐴 to every element of dom 𝐹). (Contributed by Mario Carneiro, 3-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ (𝐴 ∈ ℂ → dom (𝐹 shift 𝐴) = {𝑥 ∈ ℂ ∣ (𝑥 − 𝐴) ∈ dom 𝐹})
Theorem	shftfib 15089	Value of a fiber of the relation 𝐹. (Contributed by Mario Carneiro, 4-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐹 shift 𝐴) “ {𝐵}) = (𝐹 “ {(𝐵 − 𝐴)}))
Theorem	shftfn 15090*	Functionality and domain of a sequence shifted by 𝐴. (Contributed by NM, 20-Jul-2005.) (Revised by Mario Carneiro, 3-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐹 Fn 𝐵 ∧ 𝐴 ∈ ℂ) → (𝐹 shift 𝐴) Fn {𝑥 ∈ ℂ ∣ (𝑥 − 𝐴) ∈ 𝐵})
Theorem	shftval 15091	Value of a sequence shifted by 𝐴. (Contributed by NM, 20-Jul-2005.) (Revised by Mario Carneiro, 4-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐹 shift 𝐴)‘𝐵) = (𝐹‘(𝐵 − 𝐴)))
Theorem	shftval2 15092	Value of a sequence shifted by 𝐴 − 𝐵. (Contributed by NM, 20-Jul-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → ((𝐹 shift (𝐴 − 𝐵))‘(𝐴 + 𝐶)) = (𝐹‘(𝐵 + 𝐶)))
Theorem	shftval3 15093	Value of a sequence shifted by 𝐴 − 𝐵. (Contributed by NM, 20-Jul-2005.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐹 shift (𝐴 − 𝐵))‘𝐴) = (𝐹‘𝐵))
Theorem	shftval4 15094	Value of a sequence shifted by -𝐴. (Contributed by NM, 18-Aug-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐹 shift -𝐴)‘𝐵) = (𝐹‘(𝐴 + 𝐵)))
Theorem	shftval5 15095	Value of a shifted sequence. (Contributed by NM, 19-Aug-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐹 shift 𝐴)‘(𝐵 + 𝐴)) = (𝐹‘𝐵))
Theorem	shftf 15096*	Functionality of a shifted sequence. (Contributed by NM, 19-Aug-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐹:𝐵⟶𝐶 ∧ 𝐴 ∈ ℂ) → (𝐹 shift 𝐴):{𝑥 ∈ ℂ ∣ (𝑥 − 𝐴) ∈ 𝐵}⟶𝐶)
Theorem	2shfti 15097	Composite shift operations. (Contributed by NM, 19-Aug-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐹 shift 𝐴) shift 𝐵) = (𝐹 shift (𝐴 + 𝐵)))
Theorem	shftidt2 15098	Identity law for the shift operation. (Contributed by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ (𝐹 shift 0) = (𝐹 ↾ ℂ)
Theorem	shftidt 15099	Identity law for the shift operation. (Contributed by NM, 19-Aug-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ (𝐴 ∈ ℂ → ((𝐹 shift 0)‘𝐴) = (𝐹‘𝐴))
Theorem	shftcan1 15100	Cancellation law for the shift operation. (Contributed by NM, 4-Aug-2005.) (Revised by Mario Carneiro, 5-Nov-2013.)
⊢ 𝐹 ∈ V    ⇒   ⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (((𝐹 shift 𝐴) shift -𝐴)‘𝐵) = (𝐹‘𝐵))