Nuprl Lemma : straight-angle-sum2_symm
∀e:EuclideanPlane. ∀a,b,c,x,y,z,i,j,k:Point.  (abc + xyz ≅ ijk ⇒ out(b ac) ⇒ (x-y-z ⇐⇒ i-j-k))
Proof
Definitions occuring in Statement : 
hp-angle-sum: abc + xyz ≅ def, 
geo-out: out(p ab), 
euclidean-plane: EuclideanPlane, 
geo-strict-between: a-b-c, 
geo-point: Point, 
all: ∀x:A. B[x], 
iff: P ⇐⇒ Q, 
implies: P ⇒ Q
Definitions unfolded in proof : 
all: ∀x:A. B[x], 
implies: P ⇒ Q, 
iff: P ⇐⇒ Q, 
and: P ∧ Q, 
hp-angle-sum: abc + xyz ≅ def, 
exists: ∃x:A. B[x], 
geo-cong-angle: abc ≅a xyz, 
cand: A c∧ B, 
member: t ∈ T, 
basic-geometry: BasicGeometry, 
geo-strict-between: a-b-c, 
geo-out: out(p ab), 
uall: ∀[x:A]. B[x], 
subtype_rel: A ⊆r B, 
guard: {T}, 
uimplies: b supposing a, 
prop: ℙ, 
rev_implies: P ⇐ Q, 
basic-geometry-: BasicGeometry-, 
euclidean-plane: EuclideanPlane, 
or: P ∨ Q, 
not: ¬A, 
false: False, 
stable: Stable{P}, 
geo-eq: a ≡ b
Lemmas referenced : 
geo-sep-sym, 
angle-cong-preserves-zero-angle, 
geo-cong-angle-symm2, 
geo-strict-between_wf, 
euclidean-plane-structure-subtype, 
euclidean-plane-subtype, 
subtype_rel_transitivity, 
euclidean-plane_wf, 
euclidean-plane-structure_wf, 
geo-primitives_wf, 
geo-out_wf, 
hp-angle-sum_wf, 
geo-point_wf, 
angle-cong-preserves-straight-angle, 
geo-between-symmetry, 
geo-strict-between-implies-between, 
extended-out-preserves-between, 
geo-out_inversion, 
geo-strict-between-sym, 
geo-between-inner-trans, 
stable__geo-between, 
false_wf, 
geo-sep_wf, 
not_wf, 
geo-between_wf, 
istype-void, 
minimal-double-negation-hyp-elim, 
geo-out_functionality, 
geo-eq_weakening, 
geo-strict-between_functionality, 
geo-between_functionality, 
geo-cong-angle_functionality, 
minimal-not-not-excluded-middle, 
geo-between-middle-or, 
geo-between-exchange3, 
geo-between-exchange4, 
geo-between-outer-trans, 
geo-out-iff-between1, 
geo-between-outer-trans-cpy, 
geo-not-bet-and-out
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
lambdaFormation_alt, 
independent_pairFormation, 
sqequalHypSubstitution, 
productElimination, 
thin, 
cut, 
introduction, 
extract_by_obid, 
dependent_functionElimination, 
hypothesisEquality, 
independent_functionElimination, 
hypothesis, 
sqequalRule, 
because_Cache, 
universeIsType, 
isectElimination, 
applyEquality, 
instantiate, 
independent_isectElimination, 
inhabitedIsType, 
setElimination, 
rename, 
unionEquality, 
functionEquality, 
functionIsType, 
unionIsType, 
unionElimination, 
voidElimination
Latex:
\mforall{}e:EuclideanPlane.  \mforall{}a,b,c,x,y,z,i,j,k:Point.    (abc  +  xyz  \mcong{}  ijk  {}\mRightarrow{}  out(b  ac)  {}\mRightarrow{}  (x-y-z  \mLeftarrow{}{}\mRightarrow{}  i-j-k))
Date html generated:
2019_10_16-PM-02_05_21
Last ObjectModification:
2019_06_24-AM-10_32_07
Theory : euclidean!plane!geometry
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