Nuprl Lemma : lsep-opposite-iff
∀g:OrientedPlane. ∀a,b,x,y:Point.
  (x # ab ⇒ y # ab ⇒ (∃z:Point. (x_z_y ∧ Colinear(z;a;b)) ⇐⇒ x leftof ab ⇐⇒ y leftof ba))
Proof
Definitions occuring in Statement : 
oriented-plane: OrientedPlane, 
geo-lsep: a # bc, 
geo-colinear: Colinear(a;b;c), 
geo-left: a leftof bc, 
geo-between: a_b_c, 
geo-point: Point, 
all: ∀x:A. B[x], 
exists: ∃x:A. B[x], 
iff: P ⇐⇒ Q, 
implies: P ⇒ Q, 
and: P ∧ Q
Definitions unfolded in proof : 
so_apply: x[s], 
so_lambda: λ2x.t[x], 
uimplies: b supposing a, 
guard: {T}, 
subtype_rel: A ⊆r B, 
false: False, 
not: ¬A, 
rev_implies: P ⇐ Q, 
oriented-plane: Error :oriented-plane, 
uall: ∀[x:A]. B[x], 
prop: ℙ, 
member: t ∈ T, 
or: P ∨ Q, 
geo-lsep: a # bc, 
exists: ∃x:A. B[x], 
and: P ∧ Q, 
iff: P ⇐⇒ Q, 
implies: P ⇒ Q, 
all: ∀x:A. B[x], 
cand: A c∧ B, 
euclidean-geometry: Error :euclidean-geometry
Lemmas referenced : 
geo-lsep_wf, 
iff_wf, 
geo-colinear_wf, 
geo-between_wf, 
Error :basic-geo-primitives_wf, 
Error :basic-geo-structure_wf, 
basic-geometry-_wf, 
Error :oriented-plane_wf, 
subtype_rel_transitivity, 
Error :oriented-plane-subtype, 
basic-geometry--subtype, 
geo-point_wf, 
exists_wf, 
not-left-and-right, 
geo-left_wf, 
left-between-weak, 
Error :use-plane-sep, 
lsep-symmetry, 
lsep-symmetry2, 
Error :euclidean-geometry_wf, 
subtype_rel_self
Rules used in proof : 
productEquality, 
lambdaEquality, 
sqequalRule, 
independent_isectElimination, 
instantiate, 
applyEquality, 
voidElimination, 
independent_functionElimination, 
dependent_functionElimination, 
hypothesisEquality, 
hypothesis, 
because_Cache, 
rename, 
setElimination, 
isectElimination, 
extract_by_obid, 
introduction, 
cut, 
unionElimination, 
thin, 
productElimination, 
sqequalHypSubstitution, 
independent_pairFormation, 
lambdaFormation, 
sqequalReflexivity, 
computationStep, 
sqequalTransitivity, 
sqequalSubstitution, 
inlFormation, 
inrFormation, 
dependent_pairFormation
Latex:
\mforall{}g:OrientedPlane.  \mforall{}a,b,x,y:Point.
    (x  \#  ab  {}\mRightarrow{}  y  \#  ab  {}\mRightarrow{}  (\mexists{}z:Point.  (x\_z\_y  \mwedge{}  Colinear(z;a;b))  \mLeftarrow{}{}\mRightarrow{}  x  leftof  ab  \mLeftarrow{}{}\mRightarrow{}  y  leftof  ba))
Date html generated:
2017_10_02-PM-04_47_39
Last ObjectModification:
2017_08_05-AM-10_20_20
Theory : euclidean!plane!geometry
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