Nuprl Lemma : rv-compass-compass-lemma
∀a,b,c,d:ℝ^2.
  (a ≠ c
  ⇒ (↓∃p,q:ℝ^2. (((d(a;b) = d(a;p)) ∧ (d(c;d) = d(c;q))) ∧ (d(c;p) ≤ d(c;d)) ∧ (d(a;q) ≤ d(a;b))))
  ⇒ (∃u,v:{p:ℝ^2| ab=ap ∧ cd=cp} 
       ((↓∃p,q:ℝ^2. (((d(a;b) = d(a;p)) ∧ (d(c;d) = d(c;q))) ∧ (d(c;p) < d(c;d)) ∧ (d(a;q) < d(a;b))))
       ⇒ (r2-left(u;c;a) ∧ r2-left(v;a;c)))))
Proof
Definitions occuring in Statement : 
r2-left: r2-left(p;q;r), 
real-vec-sep: a ≠ b, 
rv-congruent: ab=cd, 
real-vec-dist: d(x;y), 
real-vec: ℝ^n, 
rleq: x ≤ y, 
rless: x < y, 
req: x = y, 
all: ∀x:A. B[x], 
exists: ∃x:A. B[x], 
squash: ↓T, 
implies: P ⇒ Q, 
and: P ∧ Q, 
set: {x:A| B[x]} , 
natural_number: $n
Definitions unfolded in proof : 
all: ∀x:A. B[x], 
implies: P ⇒ Q, 
member: t ∈ T, 
uall: ∀[x:A]. B[x], 
real-vec-dist: d(x;y), 
prop: ℙ, 
nat: ℕ, 
le: A ≤ B, 
and: P ∧ Q, 
less_than': less_than'(a;b), 
false: False, 
not: ¬A, 
so_lambda: λ2x.t[x], 
subtype_rel: A ⊆r B, 
so_apply: x[s], 
rless: x < y, 
sq_exists: ∃x:{A| B[x]}, 
real-vec-sep: a ≠ b, 
uimplies: b supposing a, 
iff: P ⇐⇒ Q, 
rev_implies: P ⇐ Q, 
uiff: uiff(P;Q), 
rev_uimplies: rev_uimplies(P;Q), 
squash: ↓T, 
sq_stable: SqStable(P), 
exists: ∃x:A. B[x], 
true: True, 
guard: {T}, 
rge: x ≥ y, 
cand: A c∧ B, 
req_int_terms: t1 ≡ t2, 
top: Top, 
rv-congruent: ab=cd, 
real-vec-add: X + Y, 
real-vec-sub: X - Y, 
req-vec: req-vec(n;x;y), 
real-vec: ℝ^n, 
nat_plus: ℕ+, 
less_than: a < b, 
or: P ∨ Q, 
r2-left: r2-left(p;q;r), 
r2-det: |pqr|, 
int_seg: {i..j-}, 
lelt: i ≤ j < k
Lemmas referenced : 
rv-circle-circle-lemma2', 
real-vec-dist_wf, 
real-vec-sub_wf, 
squash_wf, 
exists_wf, 
real-vec_wf, 
false_wf, 
le_wf, 
req_wf, 
real_wf, 
rleq_wf, 
int-to-real_wf, 
real-vec-sep_wf, 
rnexp_wf, 
radd_wf, 
rsub_wf, 
rmul_wf, 
rless_functionality, 
req_weakening, 
real-vec-dist-symmetry, 
rleq_functionality, 
rnexp_functionality, 
radd_functionality, 
rsub_functionality, 
rmul_functionality, 
sq_stable__rleq, 
rnexp-rleq, 
real-vec-dist-nonneg, 
real-vec-triangle-inequality, 
true_wf, 
radd_comm_eq, 
iff_weakening_equal, 
rleq_functionality_wrt_implies, 
rleq_weakening_equal, 
radd_functionality_wrt_rleq, 
rabs_wf, 
zero-rleq-rabs, 
rabs-difference-bound-rleq, 
radd-preserves-rleq, 
radd_comm, 
itermSubtract_wf, 
itermAdd_wf, 
itermVar_wf, 
req-iff-rsub-is-0, 
real_polynomial_null, 
real_term_value_sub_lemma, 
real_term_value_add_lemma, 
real_term_value_var_lemma, 
real_term_value_const_lemma, 
rnexp2-nonneg, 
req_inversion, 
rabs-rnexp, 
rabs-of-nonneg, 
rminus_wf, 
radd-rminus-both, 
itermMinus_wf, 
req_transitivity, 
rminus_functionality, 
real_term_value_minus_lemma, 
equal_wf, 
itermMultiply_wf, 
itermConstant_wf, 
rnexp2, 
real_term_value_mul_lemma, 
req_functionality, 
rleq-implies-rleq, 
rmul-nonneg-case1, 
radd-zero, 
real-vec-add_wf, 
rv-congruent_wf, 
rless_wf, 
r2-left_wf, 
int_seg_wf, 
real-vec-norm_wf, 
real-vec-norm_functionality, 
sq_stable__rless, 
rnexp-rless, 
less_than_wf, 
radd-rminus-assoc, 
radd-preserves-rless, 
rless_transitivity2, 
rabs-difference-bound-iff, 
rless_functionality_wrt_implies, 
rless-implies-rless, 
rmul-is-positive, 
rless_transitivity1, 
rleq_weakening, 
r2-det_wf, 
lelt_wf
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
lambdaFormation, 
cut, 
introduction, 
extract_by_obid, 
sqequalHypSubstitution, 
dependent_functionElimination, 
thin, 
isectElimination, 
because_Cache, 
hypothesisEquality, 
hypothesis, 
independent_functionElimination, 
dependent_set_memberEquality, 
natural_numberEquality, 
sqequalRule, 
independent_pairFormation, 
lambdaEquality, 
productEquality, 
applyEquality, 
setElimination, 
rename, 
setEquality, 
independent_isectElimination, 
productElimination, 
imageElimination, 
imageMemberEquality, 
baseClosed, 
equalityTransitivity, 
equalitySymmetry, 
universeEquality, 
approximateComputation, 
int_eqEquality, 
intEquality, 
isect_memberEquality, 
voidElimination, 
voidEquality, 
dependent_pairFormation, 
functionEquality, 
inlFormation, 
promote_hyp
Latex:
\mforall{}a,b,c,d:\mBbbR{}\^{}2.
    (a  \mneq{}  c
    {}\mRightarrow{}  (\mdownarrow{}\mexists{}p,q:\mBbbR{}\^{}2.  (((d(a;b)  =  d(a;p))  \mwedge{}  (d(c;d)  =  d(c;q)))  \mwedge{}  (d(c;p)  \mleq{}  d(c;d))  \mwedge{}  (d(a;q)  \mleq{}  d(a;b))))
    {}\mRightarrow{}  (\mexists{}u,v:\{p:\mBbbR{}\^{}2|  ab=ap  \mwedge{}  cd=cp\}  
              ((\mdownarrow{}\mexists{}p,q:\mBbbR{}\^{}2
                      (((d(a;b)  =  d(a;p))  \mwedge{}  (d(c;d)  =  d(c;q)))  \mwedge{}  (d(c;p)  <  d(c;d))  \mwedge{}  (d(a;q)  <  d(a;b))))
              {}\mRightarrow{}  (r2-left(u;c;a)  \mwedge{}  r2-left(v;a;c)))))
 Date html generated: 
2017_10_03-AM-11_53_00
 Last ObjectModification: 
2017_08_13-PM-00_48_29
Theory : reals
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