Nuprl Lemma : setmem-natset
∀n:ℕ. ∀x:Set{i:l}.  ((x ∈ natset(n)) ⇐⇒ ∃i:ℕn. seteq(x;natset(i)))
Proof
Definitions occuring in Statement : 
natset: natset(n), 
Set: Set{i:l}, 
setmem: (x ∈ s), 
seteq: seteq(s1;s2), 
int_seg: {i..j-}, 
nat: ℕ, 
all: ∀x:A. B[x], 
exists: ∃x:A. B[x], 
iff: P ⇐⇒ Q, 
natural_number: $n
Definitions unfolded in proof : 
assert: ↑b, 
bnot: ¬bb, 
it: ⋅, 
unit: Unit, 
bool: 𝔹, 
bfalse: ff, 
btrue: tt, 
ifthenelse: if b then t else f fi , 
uiff: uiff(P;Q), 
sq_type: SQType(T), 
emptyset: {}, 
natset: natset(n), 
or: P ∨ Q, 
decidable: Dec(P), 
so_apply: x[s], 
so_lambda: λ2x.t[x], 
top: Top, 
satisfiable_int_formula: satisfiable_int_formula(fmla), 
uimplies: b supposing a, 
lelt: i ≤ j < k, 
int_seg: {i..j-}, 
guard: {T}, 
exists: ∃x:A. B[x], 
rev_implies: P ⇐ Q, 
not: ¬A, 
false: False, 
less_than': less_than'(a;b), 
le: A ≤ B, 
nat: ℕ, 
subtype_rel: A ⊆r B, 
uall: ∀[x:A]. B[x], 
prop: ℙ, 
member: t ∈ T, 
implies: P ⇒ Q, 
and: P ∧ Q, 
iff: P ⇐⇒ Q, 
all: ∀x:A. B[x]
Lemmas referenced : 
int_formula_prop_eq_lemma, 
intformeq_wf, 
decidable__equal_int, 
int_subtype_base, 
assert-bnot, 
bool_cases_sqequal, 
equal_wf, 
lelt_wf, 
decidable__lt, 
or_wf, 
assert_of_bnot, 
iff_weakening_uiff, 
iff_transitivity, 
eqff_to_assert, 
assert_of_lt_int, 
eqtt_to_assert, 
bool_subtype_base, 
bool_wf, 
subtype_base_sq, 
bool_cases, 
plus-set_wf, 
emptyset_wf, 
primrec_wf, 
setmem-plus-set, 
not_wf, 
bnot_wf, 
assert_wf, 
lt_int_wf, 
primrec-unroll, 
setmem-mkset-sq, 
primrec0_lemma, 
nat_wf, 
primrec-wf2, 
less_than_wf, 
set_wf, 
int_seg_subtype_nat, 
int_term_value_subtract_lemma, 
itermSubtract_wf, 
subtract_wf, 
iff_wf, 
all_wf, 
int_formula_prop_not_lemma, 
intformnot_wf, 
decidable__le, 
Set_wf, 
seteq_wf, 
int_seg_wf, 
exists_wf, 
int_formula_prop_wf, 
int_formula_prop_le_lemma, 
int_term_value_constant_lemma, 
int_term_value_var_lemma, 
int_formula_prop_less_lemma, 
int_formula_prop_and_lemma, 
intformle_wf, 
itermConstant_wf, 
itermVar_wf, 
intformless_wf, 
intformand_wf, 
full-omega-unsat, 
int_seg_properties, 
le_wf, 
false_wf, 
natset_wf, 
set-subtype-coSet, 
setmem_wf
Rules used in proof : 
inrFormation, 
inlFormation, 
equalityElimination, 
promote_hyp, 
orFunctionality, 
addLevel, 
impliesFunctionality, 
equalitySymmetry, 
equalityTransitivity, 
universeEquality, 
cumulativity, 
instantiate, 
unionElimination, 
voidEquality, 
voidElimination, 
isect_memberEquality, 
dependent_functionElimination, 
intEquality, 
int_eqEquality, 
lambdaEquality, 
dependent_pairFormation, 
independent_functionElimination, 
approximateComputation, 
independent_isectElimination, 
rename, 
setElimination, 
productElimination, 
because_Cache, 
natural_numberEquality, 
dependent_set_memberEquality, 
sqequalRule, 
hypothesis, 
applyEquality, 
hypothesisEquality, 
isectElimination, 
sqequalHypSubstitution, 
extract_by_obid, 
introduction, 
independent_pairFormation, 
thin, 
cut, 
lambdaFormation, 
sqequalReflexivity, 
computationStep, 
sqequalTransitivity, 
sqequalSubstitution
Latex:
\mforall{}n:\mBbbN{}.  \mforall{}x:Set\{i:l\}.    ((x  \mmember{}  natset(n))  \mLeftarrow{}{}\mRightarrow{}  \mexists{}i:\mBbbN{}n.  seteq(x;natset(i)))
 Date html generated: 
2018_07_29-AM-10_03_03
 Last ObjectModification: 
2018_07_11-PM-05_49_21
Theory : constructive!set!theory
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