اذا كانت الزاويتان متكاملتان فإنهما متجاورتان على مستقيم واحد. دائرة

neu bearbeitete und erweiterte Auflage 2007, Korrigierter Nachdruck 2009, , S	Springer, Berlin, Heidelberg, New York,
The Associated Harmonic Quadrilateral, Paris Pamfilos, Forum Geometricorum, Volume 14 2014 15—29	Verlag Harri German, 5th edition, Thun and Frankfurt 2001, p

دائرة

Smith, Geoff, and Leversha, Gerry, "Euler and triangle geometry", Mathematical Gazette 91, November 2007, 436—452.

دائرة: Marie-Nicole Gras, "Distances between the circumcenter of the extouch triangle and the classical centers", Forum Geometricorum 14 2014 , 51-61
دائرة: 3 in Introduction to Geometry, 2nd ed
دائرة: Nelson, Roger, "Euler's triangle inequality via proof without words," Mathematics Magazine 81 1 , February 2008, 58-61

"The Evolution of the Isoperimetric Problem"	"On the areas of cyclic and semicyclic polygons" PDF
in modern notation, with introductory chapters	Advanced Euclidean Geometry: An Elementary treatise on the geometry of the Triangle and the Circle

, "Some impossible constructions in elementary geometry", Mathematical Gazette 88, November 2004, 548—551.

دائرة: Martin Celli, "A Proof of the Butterfly Theorem Using the Similarity Factor of the Two Wings", 16, 2016, 337—338
دائرة: Youschkevitch, chief editor: Boris A
دائرة: See in particular the bottom of p

Courant and Robbins 1996, p
Washington, DC, USA: Mathematical Association of America	Michael Henle, "Modern Geometry: Non-Euclidean, Projective, and Discrete", 2nd edition, , 2001• The Secrets of Triangles, Prometheus Books, 2012

Novi Commentarii academiae scientarum imperialis Petropolitanae.

دائرة: , The Elements of Geometry, in Eight Books; or, First Step in Applied Logic London, Longmans, Green, Reader and Dyer, 1874 , p
دائرة: Science in the Ancient World: An Encyclopedia
دائرة: Proceedings of the Royal Irish Academy