@MISC{EUCLID13.MIZ,
  AUTHOR = {Coghetto, Roland},
  TITLE = {Altitude, Orthocenter of a Triangle and Triangulation},
  DAY = {30},
  MONTH = {December},
  YEAR = {2015},
  SECTION1 = {Preliminaries},
  SECTION2 = {Orthocenter},
  SECTION3 = {Triangulation},
  ADDRESS1 = {Rue de la Brasserie 5\\7100 La Louvi\`ere, Belgium},
  MSC2010 = {51M04,3B035},
  KEYWORDS = {Euclidean geometry, trigonometry,
              altitude, orthocenter, triangulation, distance},
  SUMMARY = {We introduce the altitudes of a triangle
             (the cevians perpendicular to the opposite sides).
  Using the generalized Ceva's Theorem, we prove the existence
  and uniqueness of the orthocenter of a triangle \cite{Coxeter:1967}.
  Finally, we formalize in Mizar \cite{Mizar:2015}
  some formulas \cite{campbell1956trigonometrie}
  to calculate distance using triangulation.}}

@BOOK{Coxeter:1967,
 AUTHOR={Coxeter, H.S.M., Greitzer, S.L.},
 TITLE={Geometry Revisited},
 PUBLISHER={The Mathematical Association of America (Inc.)},
 PAGES={5},
 YEAR=1967}

@BOOK{campbell1956trigonometrie,
  title={La trigonom{\'e}trie},
  author={Campbell, R.},
  series={Que sais-je?},
  year={1956},
  publisher={Presses universitaires de France}}

@inproceedings{Mizar:2015,
  author    = {Bancerek, Grzegorz and
               Byli{\'n}ski, Czes{\l}aw and
               Grabowski, Adam and
               Korni{\l}owicz, Artur and
               Matuszewski, Roman and
               Naumowicz, Adam and
               P\c{a}k, Karol and
               Urban, Josef},
  title     = {Mizar: State-of-the-art and Beyond},
  booktitle = {Intelligent Computer Mathematics -- International Conference,
               {CICM} 2015, Washington, DC, USA, July 13--17, 2015, Proceedings},
  pages     = {261--279},
  year      = {2015},
  crossref  = {DBLP:conf/mkm/2015},
  url       = {http://dx.doi.org/10.1007/978-3-319-20615-8_17},
  doi       = {10.1007/978-3-319-20615-8_17}}

