Books & editorial activities

Books (electronically available or not)

  • Virgul Nicula, Cosmin Pohoata, The Harmonic Division, GIL, 2007 (110 pages - in Romanian).
    Let A, B, C, D be four points lying in this order on a given line. The quadruple (A, B, C, D) is called harmonic division if and only if BA/BC=-DA/DC, or in terms of cross-ratios, (A, B, C, D)=-1. Since harmonic divisions instantly imply the use of notions like poles and polars, projections, inversions and so on, we’ve planned this book to be a problem solving introduction in synthetic projective geometry. The problems we discuss here are mainly from international competitions (like the IMO - International Mathematical Olympiad and the BMO - Balkan Mathematical Olympiad), from national IMO/BMO team selection tests and from national olympiads. The problems are usually associated with at least two solutions, for a better comparison between the “synthetic approach” and other methods like trigonometry or analytical geometry.
  • Mihai Baluna, Iurie Boreico, Andrei Frimu, Andrei Ciupan, Cosmin Pohoata, Romanian Mathematical Olympiads From 2007, GIL, 2007 (192 pages - in Romanian).
    This book contains (new) solutions for the problems given in 2007 at the Romanian National Olympiads/Contests.
  • Vo Quoc Ba Can, Cosmin Pohoata, Old and New Inequalities. Volume 2, GIL, 2008 (160 pages - in English).
    In this book we present a large variety of problems involving new inequalities, questions that became famous in recent (mathematical) competitions or journals because of their beauty and difficulty. Some of the introductory problems we chose to discuss are known, but we have included them here with new solutions which show the diversity of ideas pertaining to inequalities. The most important prerequisite for benefiting from this book is the desire to master the craft of discovery and proof. The formal requirements are quite modest. Anyone who knows basic inequalities such as the ones of Cauchy-Schwarz, Holder, Schur, Chebyshev or Bernoulli is well prepared for almost everything to be found here. The book is dedicated to high-school students preparing for the IMO (International Mathematical Olympiad), to their teachers or instructors, and, of course, to anyone interested in Inequalities.
  • Vlad Matei, Cosmin Pohoata, Radu Titiu, Catalin Turcas, Romanian Mathematical Olympiads From 2008, GIL, 2008 (280 pages - in Romanian).
    This book contains (new) solutions for the problems given in 2008 at the Romanian National Olympiads/Contests.
  • Hojoo Lee, Tom Lovering, Cosmin Pohoata, Infinity, online publication, 2008 (204 pages - in English; downloadable from http://www.cpohoata.com/2008/10/17/infinity/ and/or http://ideahitme.wordpress.com/infinity/).
    This weblication is organized in series of lecture notes in (Combinatorial or not) Number Theory, Geometry, Inequalities, which are destinated to high-school students preparing for the IMO (International Mathematical Olympiad), to their teachers/instructors, and, of course, to anyone who hasn’t lost his passion for elementary mathematics.

Editorial activities:

  • moderator of the MathLinks Forum (perhaps the largest and most popular online mathematical community - created and maintained by Valentin Vornicu).
  • moderator of Foro de Geometria (a lovely forum dedicated to Euclidean Geometry - unfortunately,  the language which is frequently used is Spanish).

| Category: Articles, papers, notes in Euclidean Geometry