Step * 1 of Lemma Euclid-Prop21


1. EuclideanPlane
2. Point
3. Point
4. Point
5. Point
6. I(abc;d)
⊢ {|cd| |bd| < |ba| |ac| ∧ bac < bdc}
BY
(Unfold `geo-interior-point` -1
   THEN (Assert leftof bd BY
               (InstLemma `left-symmetry`  [⌜g⌝;⌜d⌝;⌜a⌝;⌜b⌝]⋅ THEN Auto))
   THEN (Assert leftof db BY
               (InstLemma `left-all-symmetry`  [⌜g⌝;⌜d⌝;⌜b⌝;⌜c⌝]⋅ THEN Auto))) }

1
1. EuclideanPlane
2. Point
3. Point
4. Point
5. Point
6. leftof bc ∧ leftof bc ∧ leftof ca ∧ leftof ab
7. leftof bd
8. leftof db
⊢ {|cd| |bd| < |ba| |ac| ∧ bac < bdc}


Latex:


Latex:

1.  g  :  EuclideanPlane
2.  a  :  Point
3.  b  :  Point
4.  c  :  Point
5.  d  :  Point
6.  I(abc;d)
\mvdash{}  \{|cd|  +  |bd|  <  |ba|  +  |ac|  \mwedge{}  bac  <  bdc\}


By


Latex:
(Unfold  `geo-interior-point`  -1
  THEN  (Assert  a  leftof  bd  BY
                          (InstLemma  `left-symmetry`    [\mkleeneopen{}g\mkleeneclose{};\mkleeneopen{}d\mkleeneclose{};\mkleeneopen{}a\mkleeneclose{};\mkleeneopen{}b\mkleeneclose{}]\mcdot{}  THEN  Auto))
  THEN  (Assert  c  leftof  db  BY
                          (InstLemma  `left-all-symmetry`    [\mkleeneopen{}g\mkleeneclose{};\mkleeneopen{}d\mkleeneclose{};\mkleeneopen{}b\mkleeneclose{};\mkleeneopen{}c\mkleeneclose{}]\mcdot{}  THEN  Auto)))




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