Nuprl Lemma : r2-det-nonzero
∀p,q,r:ℝ^2.  (rv-pos-angle(2;p;q;r) ⇒ |pqr| ≠ r0)
Proof
Definitions occuring in Statement : 
r2-det: |pqr|, 
rv-pos-angle: rv-pos-angle(n;a;b;c), 
real-vec: ℝ^n, 
rneq: x ≠ y, 
int-to-real: r(n), 
all: ∀x:A. B[x], 
implies: P ⇒ Q, 
natural_number: $n
Definitions unfolded in proof : 
all: ∀x:A. B[x], 
implies: P ⇒ Q, 
rv-pos-angle: rv-pos-angle(n;a;b;c), 
member: t ∈ T, 
prop: ℙ, 
uall: ∀[x:A]. B[x], 
nat: ℕ, 
le: A ≤ B, 
and: P ∧ Q, 
less_than': less_than'(a;b), 
false: False, 
not: ¬A, 
real-vec-sub: X - Y, 
r2-det: |pqr|, 
real-vec: ℝ^n, 
int_seg: {i..j-}, 
lelt: i ≤ j < k, 
less_than: a < b, 
squash: ↓T, 
true: True, 
uimplies: b supposing a, 
rsub: x - y, 
uiff: uiff(P;Q), 
rev_uimplies: rev_uimplies(P;Q), 
subtype_rel: A ⊆r B, 
iff: P ⇐⇒ Q, 
rev_implies: P ⇐ Q, 
nat_plus: ℕ+, 
dot-product: x⋅y, 
subtract: n - m, 
so_lambda: λ2x.t[x], 
rless: x < y, 
sq_exists: ∃x:{A| B[x]}, 
decidable: Dec(P), 
or: P ∨ Q, 
satisfiable_int_formula: satisfiable_int_formula(fmla), 
exists: ∃x:A. B[x], 
top: Top, 
so_apply: x[s], 
bool: 𝔹, 
unit: Unit, 
it: ⋅, 
btrue: tt, 
ifthenelse: if b then t else f fi , 
bfalse: ff, 
sq_type: SQType(T), 
guard: {T}, 
bnot: ¬bb, 
assert: ↑b, 
nequal: a ≠ b ∈ T , 
lt_int: i <z j, 
eq_int: (i =z j), 
rneq: x ≠ y
Lemmas referenced : 
rv-pos-angle_wf, 
false_wf, 
le_wf, 
real-vec_wf, 
lelt_wf, 
real_wf, 
equal_wf, 
req_wf, 
rsub_wf, 
radd_wf, 
rmul_wf, 
int-to-real_wf, 
rminus_wf, 
req_weakening, 
uiff_transitivity, 
req_functionality, 
radd_functionality, 
rminus_functionality, 
req_transitivity, 
rmul-distrib, 
rmul_over_rminus, 
rmul_comm, 
rminus-radd, 
rmul_functionality, 
rminus-rminus, 
req_inversion, 
radd-assoc, 
radd-ac, 
radd_comm, 
rminus-as-rmul, 
rmul-identity1, 
rmul-distrib2, 
radd-int, 
rmul-zero-both, 
radd-zero-both, 
r2-det_wf, 
real-vec-sub_wf, 
rless_wf, 
rabs_wf, 
dot-product_wf, 
real-vec-norm_wf, 
rneq_functionality, 
square-nonzero, 
rnexp-rless, 
zero-rleq-rabs, 
less_than_wf, 
rnexp_wf, 
rnexp2-nonneg, 
rless_functionality, 
rabs-rnexp, 
rnexp-rmul, 
real-vec-norm-squared, 
rabs-of-nonneg, 
rnexp2, 
rsum_wf, 
nat_plus_properties, 
decidable__lt, 
satisfiable-full-omega-tt, 
intformand_wf, 
intformnot_wf, 
intformless_wf, 
itermVar_wf, 
itermConstant_wf, 
itermAdd_wf, 
int_formula_prop_and_lemma, 
int_formula_prop_not_lemma, 
int_formula_prop_less_lemma, 
int_term_value_var_lemma, 
int_term_value_constant_lemma, 
int_term_value_add_lemma, 
int_formula_prop_wf, 
int_seg_wf, 
lt_int_wf, 
bool_wf, 
eqtt_to_assert, 
assert_of_lt_int, 
eqff_to_assert, 
bool_cases_sqequal, 
subtype_base_sq, 
bool_subtype_base, 
assert-bnot, 
eq_int_wf, 
assert_of_eq_int, 
int_subtype_base, 
neg_assert_of_eq_int, 
subtract_wf, 
subtract-add-cancel, 
rsum_unroll, 
rsum_single, 
radd-preserves-rless, 
rmul-assoc, 
rmul-ac
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
lambdaFormation, 
sqequalHypSubstitution, 
cut, 
introduction, 
extract_by_obid, 
isectElimination, 
thin, 
dependent_set_memberEquality, 
natural_numberEquality, 
sqequalRule, 
independent_pairFormation, 
hypothesis, 
hypothesisEquality, 
applyEquality, 
because_Cache, 
imageMemberEquality, 
baseClosed, 
equalityTransitivity, 
equalitySymmetry, 
dependent_functionElimination, 
independent_functionElimination, 
minusEquality, 
addEquality, 
independent_isectElimination, 
productElimination, 
lambdaEquality, 
setElimination, 
rename, 
unionElimination, 
dependent_pairFormation, 
int_eqEquality, 
intEquality, 
isect_memberEquality, 
voidElimination, 
voidEquality, 
computeAll, 
equalityElimination, 
promote_hyp, 
instantiate, 
cumulativity, 
inrFormation, 
addLevel
Latex:
\mforall{}p,q,r:\mBbbR{}\^{}2.    (rv-pos-angle(2;p;q;r)  {}\mRightarrow{}  |pqr|  \mneq{}  r0)
 Date html generated: 
2017_10_03-AM-11_47_05
 Last ObjectModification: 
2017_04_11-PM-05_33_14
Theory : reals
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