@MISC{EUCLID_6.MIZ,
  AUTHOR = {Riccardi, Marco},
  TITLE = {Heron's Formula and Ptolemy's Theorem},
  SECTION1 = {Law of Cosines and Meister-Gauss Formula},
  SECTION2 = {Some elementary facts about Euclidean geometry},
  SECTION3 = {Heron's Formula and Ptolemy's Theorem},
  SECTION4 = {Appendix},
  DAY = {10},
  MONTH = {January},
  YEAR = {2008},
  ADDRESS1 = {Casella Postale 49\\54038 Montignoso\\Italy},
  SUMMARY = {The goal of this article is to formalize 
  some theorems that are in the Freek Wiedijk's list "Formalizing 100 Theorems" 
  on the web. These are elementary theorems included in every handbook of 
  Euclidean geometry and trigonometry: 
  the law of cosines, the Heron's formula, the isosceles triangle theorem,
  the intersecting chords theorem and the Ptolemy's theorem.}}
