Step
*
of Lemma
congruence-preserves-lsep
∀g:EuclideanPlane. ∀a,b,c,A,B,C:Point.  (ab ≅ AB 
⇒ ac ≅ AC 
⇒ bc ≅ BC 
⇒ c # ab 
⇒ (¬¬C # AB))
BY
{ (Auto
   THEN (D 0 THENA Auto)
   THEN (RWO "not-lsep-iff-colinear" (-1) THEN Auto)
   THEN (Assert Colinear(c;a;b) BY
               EasyGeometry)
   THEN RWO "not-lsep-iff-colinear<" (-1)
   THEN Auto) }
Latex:
Latex:
\mforall{}g:EuclideanPlane.  \mforall{}a,b,c,A,B,C:Point.    (ab  \mcong{}  AB  {}\mRightarrow{}  ac  \mcong{}  AC  {}\mRightarrow{}  bc  \mcong{}  BC  {}\mRightarrow{}  c  \#  ab  {}\mRightarrow{}  (\mneg{}\mneg{}C  \#  AB))
By
Latex:
(Auto
  THEN  (D  0  THENA  Auto)
  THEN  (RWO  "not-lsep-iff-colinear"  (-1)  THEN  Auto)
  THEN  (Assert  Colinear(c;a;b)  BY
                          EasyGeometry)
  THEN  RWO  "not-lsep-iff-colinear<"  (-1)
  THEN  Auto)
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