As the title says, this blog is mainly a list of math problems. It all started as a notebook in which I wrote some of the problems I encountered and which seemed worthy to remember. Since the notebook was too small to eventually contain every interesting problem, I decided to make an online version of it. There might be some posts which can not be considered problems, as course notes, or presentation of a subject I’m interested in. Most, but not all, problems posted here have complete solutions or hints. Still, there are problems for which I haven’t written a solution, or for which I don’t know a solution (like some of the Miklos Schweitzer competition or the Open page). I hope I could present here a glimpse of the beauty of math, and that the problems presented will be helpful, inspiring and motivating in learning math.

If you have any questions, remarks, critics don’t hesitate to leave a comment or to contact me at beni22sof[at]yahoo[dot]com

If you’re interested check out my CV/Resume page and my Piano page. Also, there is a Problem List page where you can see the statements of the problems (not finished yet).

A new page was created, where I’ll post problems found in books or Internet for which I don’t have solutions yet. If you like a challenge try the Open page.

Thanks for reading my blog. Check out the Blogroll links for more math-related interesting blogs/websites.

  1. anonim
    April 2, 2011 at 2:06 am

    Multe felicitari pentru realizari! Tine-o tot asa!

  2. June 20, 2011 at 11:36 am

    Nu este nicio problema. Vom colabora pe partea de traduceri.
    Daca doresti sa incepem un proiect dupa 1.07.2011 astept un e-mail

  3. August 15, 2011 at 10:24 am

    Dear Beni Bogosel

    My first treatment of your non-standard geometry problem on math stackexchange contained a serious mistake (the function \lambda has period 2\pi, not \pi). The edited version gives a hopefully correct proof that the constant is \pi/4.

    Christian Blatter

    • August 16, 2011 at 12:07 am

      Thank you very much. 🙂

  4. VIDIANI Georges
    January 17, 2014 at 12:01 pm

    La revue mensuelle Quadrature 91 Janvier marts 2014 pose page 47 E355.
    En la cherchant je suis tombé sur votre question sur le site stackexchange.

    Dans votre article p 3 on peut vérifier que f1 ety f2 sont additives

    Il y a aussi

    et l’article de 1968 du Roumain Jaroslav Smital

    Je suis très intéréssé par toute autre référence précise


    The monthly Quadrature 91 January 2014 laying marts page 47 E355.
    In the book I came across your question on StackExchange site.

    In your article p 3 we can verify that f1 f2 and y are additive

    There is also

    and Article 1968 of the Romanian Jaroslav Smital

    I am very interested in any specific reference


    • January 17, 2014 at 1:33 pm

      Hello. I do not have acces at the Quadrature magazine you quote. In my pdf file you quote I don’t think that f_1 and f_2 are additive, but I remember seeing a proof of the fact that each additive function can be written as a sum of additive functions with Darboux property. I don’t know if that is what you are looking for.

      If you want to clarify the question or ask me anything else, I’m available.

  5. VIDIANI Georges
    January 17, 2014 at 2:23 pm

    Vidiani Fontaine Les Dijon : je suis en effet très intéressé par la preuve que toute fonction additive est la somme de deux fonctions vérifiant la propriété de Darboux.

    Voir article 16 de

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