Nuprl Lemma : subtype_rel_b-union_iff
∀[A,B,C:Type].  uiff((B ⋃ C) ⊆r A;(B ⊆r A) ∧ (C ⊆r A))
Proof
Definitions occuring in Statement : 
b-union: A ⋃ B
, 
uiff: uiff(P;Q)
, 
subtype_rel: A ⊆r B
, 
uall: ∀[x:A]. B[x]
, 
and: P ∧ Q
, 
universe: Type
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x]
, 
member: t ∈ T
, 
uiff: uiff(P;Q)
, 
and: P ∧ Q
, 
uimplies: b supposing a
, 
guard: {T}
, 
subtype_rel: A ⊆r B
, 
prop: ℙ
, 
b-union: A ⋃ B
, 
tunion: ⋃x:A.B[x]
, 
bool: 𝔹
, 
unit: Unit
, 
ifthenelse: if b then t else f fi 
, 
pi2: snd(t)
Lemmas referenced : 
subtype_rel_b-union-left, 
subtype_rel_transitivity, 
b-union_wf, 
subtype_rel_b-union-right, 
subtype_rel_wf, 
and_wf
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
isect_memberFormation, 
introduction, 
cut, 
independent_pairFormation, 
sqequalHypSubstitution, 
lemma_by_obid, 
isectElimination, 
thin, 
hypothesisEquality, 
hypothesis, 
because_Cache, 
independent_isectElimination, 
sqequalRule, 
productElimination, 
independent_pairEquality, 
axiomEquality, 
isect_memberEquality, 
equalityTransitivity, 
equalitySymmetry, 
universeEquality, 
lambdaEquality, 
imageElimination, 
unionElimination, 
equalityElimination, 
applyEquality
Latex:
\mforall{}[A,B,C:Type].    uiff((B  \mcup{}  C)  \msubseteq{}r  A;(B  \msubseteq{}r  A)  \mwedge{}  (C  \msubseteq{}r  A))
Date html generated:
2016_05_13-PM-03_57_54
Last ObjectModification:
2015_12_26-AM-10_52_04
Theory : bool_1
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