Nuprl Lemma : cross-product-equal-0-iff
∀r:IntegDom{i}. ∀a,b:ℕ3 ⟶ |r|.
  ((∀x,y:|r|.  Dec(x = y ∈ |r|))
  ⇒ ((a x b) = 0 ∈ (ℕ3 ⟶ |r|)
     ⇐⇒ (a = 0 ∈ (ℕ3 ⟶ |r|)) ∨ (b = 0 ∈ (ℕ3 ⟶ |r|)) ∨ (∀l:ℕ3 ⟶ |r|. ((a . l) = 0 ∈ |r| ⇐⇒ (b . l) = 0 ∈ |r|))))
Proof
Definitions occuring in Statement : 
scalar-product: (a . b), 
cross-product: (a x b), 
zero-vector: 0, 
int_seg: {i..j-}, 
decidable: Dec(P), 
all: ∀x:A. B[x], 
iff: P ⇐⇒ Q, 
implies: P ⇒ Q, 
or: P ∨ Q, 
function: x:A ⟶ B[x], 
natural_number: $n, 
equal: s = t ∈ T, 
integ_dom: IntegDom{i}, 
rng_zero: 0, 
rng_car: |r|
Definitions unfolded in proof : 
so_apply: x[s], 
not: ¬A, 
false: False, 
less_than': less_than'(a;b), 
le: A ≤ B, 
nat: ℕ, 
so_lambda: λ2x.t[x], 
rev_implies: P ⇐ Q, 
rng: Rng, 
crng: CRng, 
integ_dom: IntegDom{i}, 
uall: ∀[x:A]. B[x], 
prop: ℙ, 
member: t ∈ T, 
and: P ∧ Q, 
iff: P ⇐⇒ Q, 
implies: P ⇒ Q, 
all: ∀x:A. B[x], 
guard: {T}, 
or: P ∨ Q, 
uimplies: b supposing a, 
subtype_rel: A ⊆r B, 
infix_ap: x f y, 
squash: ↓T, 
true: True, 
exists: ∃x:A. B[x], 
integ_dom_p: IsIntegDom(r), 
decidable: Dec(P), 
sq_exists: ∃x:A [B[x]]
Lemmas referenced : 
integ_dom_wf, 
decidable_wf, 
rng_zero_wf, 
le_wf, 
false_wf, 
scalar-product_wf, 
iff_wf, 
all_wf, 
or_wf, 
zero-vector_wf, 
cross-product_wf, 
rng_car_wf, 
int_seg_wf, 
equal_wf, 
cross-product-equal-0, 
rng_times_zero, 
iff_weakening_equal, 
rng_times_wf, 
squash_wf, 
true_wf, 
scalar-product-mul, 
crng_times_comm, 
cross-product-0, 
not_wf, 
cross-product-non-zero-implies-ext, 
compact-finite, 
decidable__equal_compact_domain, 
rng_sig_wf, 
mul-zero-vector, 
rng_one_wf, 
rng_minus_wf, 
cross-product-anti-comm, 
vector-mul_wf
Rules used in proof : 
dependent_set_memberEquality, 
lambdaEquality, 
sqequalRule, 
because_Cache, 
applyEquality, 
functionExtensionality, 
hypothesisEquality, 
rename, 
setElimination, 
hypothesis, 
natural_numberEquality, 
functionEquality, 
thin, 
isectElimination, 
sqequalHypSubstitution, 
extract_by_obid, 
introduction, 
cut, 
independent_pairFormation, 
lambdaFormation, 
sqequalReflexivity, 
computationStep, 
sqequalTransitivity, 
sqequalSubstitution, 
inrFormation, 
equalitySymmetry, 
equalityTransitivity, 
inlFormation, 
unionElimination, 
productElimination, 
independent_functionElimination, 
dependent_functionElimination, 
independent_isectElimination, 
baseClosed, 
imageMemberEquality, 
levelHypothesis, 
equalityUniverse, 
imageElimination, 
applyLambdaEquality, 
universeEquality, 
productEquality, 
cumulativity, 
voidElimination
Latex:
\mforall{}r:IntegDom\{i\}.  \mforall{}a,b:\mBbbN{}3  {}\mrightarrow{}  |r|.
    ((\mforall{}x,y:|r|.    Dec(x  =  y))
    {}\mRightarrow{}  ((a  x  b)  =  0  \mLeftarrow{}{}\mRightarrow{}  (a  =  0)  \mvee{}  (b  =  0)  \mvee{}  (\mforall{}l:\mBbbN{}3  {}\mrightarrow{}  |r|.  ((a  .  l)  =  0  \mLeftarrow{}{}\mRightarrow{}  (b  .  l)  =  0))))
Date html generated:
2018_05_21-PM-09_44_10
Last ObjectModification:
2018_01_09-PM-02_07_38
Theory : matrices
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