geometry collections, articles, notes (pdf)

Here I am gonna posts geometry  articles, notes  and problem collections,  that I create or collect from sites around the internet. Free books, old and recent, are collected here.

Paris Pamfilos - Geometricon
190 pages' Sample of Geometricon, a 800 pages Geometry book in English, currently available only in Greek

Problems collections by others, from the internet

Non English problem collections

Concurrent lines, problems without words

Hans Walser - Schnittpunkte :
101-200 ,  201-300 ,  301-400 ,   401-500 ,  501-600,  601-700

problem collections that do not contain only geometry
sources:  (Tran Quang Hung)  (Amir Hossein Parvardi, David Altisio, Ercole Suppa)  (liverpool26) (mathscope, collection of inequalities)
The School Yard Olympiad facebook group (Geometri Günlüğü)

My problem collections in English

sources: (blogspot, inactive)
JUVENTUD GEÓMETRA (fb group, incactive)
JUVENTUD MATEMÁTICA (fb group, incactive)
Geito Mr.G - SobreGeometrias (blogspot, incactive) (blogspot, inactive)
Sobre Geometrias SG SX (wordpress, incactive)
Sobre Geometrias SG (fb page, incactive)
Sobre Geometrias SG SX (fb group, incactive)

Of Historic Value

Geometric Transformations
Articles - Notes 

Barycentric Coordinates
from International Journal of Computer Discovered Mathematics (

Geometry articles from:
The International Journal of Advances in Applied Mathematics and Mechanics (IJAAMM) (

Geometry articles from:
Romanian Mathematical Magazine (RMM) (
  1. Nguyen Ngoc Giang - The creation of the Steiner-Lehmus’ theorem (Ho Chi Minh City - Vietnam)
  2. Thanasis Gakopoulos - Gakopoulos' Lemmas (Greece)

Geometry Articles by Crux (collected here)

Index of Geometry Articles of  #  22 -38 (pdf links)
Recurring Crux Configurations, by J. Chris Fisher
    Focus On .., by Michel Bataille 

    Geometry Articles by Mathematical Reflections (collected here)

    1. A Characterization of the Parallelogram, by Paris Pamfilos 2016.3
    2. A Fine Use of Transformations, by Rithvik Pasumarty 2016.4
    3. A Forgotten Coaxality Lemma, by Stanisor Stefan Dan 2015.5
    4. A Generalization of the Napoleon’s Theorem, by Khakimboy Egamberganov 2017.3
    5. A Metric Relation and its Applications, by Son Hong Ta 2008.2
    6. A minimum problem, by Laurentiu Panaitopol 2006.6
    7. A new proof for Napoleon's Theorem, by Alex Anderson  2007.3
    8. A Note on Power of a Point, by Michal Rolinek & Josef Tkadlec 2010.5
    9. A Nice Theorem on Mixtilinear Incircles, by Khakimboy Egamberganov 2016.4
    10. A Note on the Malfatti Problem, by Titu Andreescu & Oleg Mushkarov 2006.4
    11. A Short Proof of Lamoen's Generalization of the Droz-Farny Line Theorem, by Cosmin Pohoata & Son Hong Ta 2011
    12. A Special Point on the Median, by Anant Mudgal & Gunmay Handa 2017.2
    13. A Way to Prove a Geometric Inequality R $\ge$ 3r, by Nguyen Tien Lam 2009.1
    14. All About Excircles!, by Prasanna Ramakrishnan 2014.6
    15. Angle Inequalities in Tetrahedra, by Mark Chen 2008.6
    16. Back to Euclidean Geometry: Droz-Farny Demystified, by Titu Andreescu & Cosmin Pohoata 2012
    17. Concyclicities in Tucker-like Configurations, by Stefan Dominte & Tudor-Dimitrie Popescu 2016.1
    18. Droz-Farny, an Inverse View, by Paris Pamfilos 2015.2
    19. Equiangular polygons: An algebraic approach, by Titu  Andreescu & Bogdan Enescu 2006.1
    20. Harmonic Division and its Applications, by Cosmin Pohoata 2007.4
    21. Inequalities on Ratios of Radii of Tangent Circles, by Y.N. Aliyev 2015.5
    22. From Baltic Way to Feuerbach - A Geometrical Excursion, by Darij Grinberg 2006.2
    23. Hartcourt’s Theorem Via Salmon’s Lemma, by Luis Gonzalez and Cosmin Pohoata 2013.6
    24. How to make a soccer ball, Euler's relation for polyhedra and planar graphs, by Bogdan Enescu 2013.4
    25. Let's Talk About Symmedians! , by Sammy Luo and Cosmin Pohoata 2013.4
    26. Newton and Midpoints of Diagonals of Circumscriptible Quadrilaterals, by Titu  Andreescu, Luis Gonzalez & Cosmin Pohoata 2014.1
    27. On a Mixtilinear Coaxality, by Cosmin Pohoata & Vladimir Zajic 2012
    28. On a vector equality, by Nguyen Tien Lam 2008.6
    29. On Casey's Inequality, by Tran Quang Hung 2011.2
    30. On Distances In Regular Polygons, by N. Javier Buitrago A. 2010.5
    31. On Fontene’s Theorems, by Marius Bocanu  2015.2
    32. On some geometric inequalities, by Tran Quang Hung 2008.3
    33. On the area of a pedal triangle, by Ivan Borsenco 2007.2
    34. On the extension of Carnot's Theorem, by Tran Quang Hung 2007.6
    35. On the Maximum Area of a Triangle With the Fixed Distances From its Vertices to a Given Point , by Ivan Borsenco, Roberto Bosch Cabrera & Daniel Lasaosa 2014.2
    36. On vector properties of an equilateral triangle, by Tran Quang Hung 2007.2
    37. Similar Quadrilaterals, by Guangqi Cui, Akshaj Kadaveru, Joshua Lee, Sagar Maheshwari 2014.5
    38. The Apollonian Circles and Isodynamic Points, by Tarik Adnan Moon 2010.6
    39. The Monge-D’Alembert Circle Theorem, by Cosmin Pohoata & Jan Vonk 2011.5
    40. The Neuberg-Mineur circle, by Darij Grinberg
    41. The Symmedian Point and Poncelet’s Porism
    42. Triangle Bordered With Squares, by Catalin Barbu 2010.4
    43. Triangles Homothetic with the Intouch Triangle, by Sava Grozdev, Hiroshi Okumura, & Deko Dekov 2018.2
    44. Vectors Conquering Hexagons, by Iurie Boreico 2008.1

    Geometry Articles by Mathematical Excalibur (collected here)

    by Kin - Yin Li
    by K. K. Kwok
    by Nguyen Ngoc Giang

    Geometry Articles  by  Revista Escolar de la Olimpíada Iberoamericana de Matemática (collected here)


    Geometry material from Canada IMO Training Site (collected here) (source:

    Adrian Tang
    Alexander Remorov
    David Arthur
    Matthew Brennan

    Lindsey Shorser
    Yufei Zhao
    Victoria Krakovna
    2018 winter camp


    The problems from the Facebook Group Romantics of Geometry in English:

    plane geometry links in FB: 001-500501-10001001-1500 , 1501-2000 , 2000-2500
    link in FB: solid geometry

    The exercises by the Romantics of Geometry in English (pdf): (not updated anymore)

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