There's this pet peeve I have where people sometimes ask things like what kind of strategies they should use for, say, collinearity problems in geometry. Like, I know there are valid answers like Menelaus or something. But the reason it bugs me is because "the problem says to prove collinearity" is about as superficial as… Continue reading Imperative statements in geometry don’t matter
Tag: olympiad
Brianchon is fair game
About five years ago I wrote a blog post warning that I thought it was a bad idea to design math olympiads to be completely untrainable, because I think math olympiads should be about talent development rather than just talent identification, yada yada yada. So now I want to say the other direction: I also… Continue reading Brianchon is fair game
Against exploitable rubrics
Editorial note: this post was mostly written in February 2023. Any resemblance to contests after that date is therefore coincidental. Background A long time ago, rubrics for the IMO and USAMO were fairly strict. Out of seven, the overall meta-rubric looks like: 7: Problem solved 6: Tiny slip (and contestant could repair) 5: Small gap… Continue reading Against exploitable rubrics
Japanese EGMO is published!
I'm happy to thank 日本評論社 and their team (Fuma Hirayama, Yuki Kumagae, Taiyo Kodama, Ayato Shukuta, among others) for making the Japanese translation a reality. As well as tripling the length of the errata PDF :) This marks the second translation of the EGMO textbook (a Chinese translation was published a while ago as well… Continue reading Japanese EGMO is published!
USEMO Problem Development, Behind the Scenes
In this post I'm hoping to say a bit about the process that's used for the problem selection of the recent USEMO: how one goes from a pool of problem proposals to a six-problem test. (How to write problems is an entirely different story, and deserves its own post.) I choose USEMO for concreteness here,… Continue reading USEMO Problem Development, Behind the Scenes
USA Special Team Selection Test Series for IMO 2021
A lot of people have been asking me how team selection is going to work for the USA this year. This information was sent out to the contestants a while ago, but I understand that there's a lot of people outside of MOP 2020 who are interested in seeing the TST problems :) so this… Continue reading USA Special Team Selection Test Series for IMO 2021
USEMO sign-ups are open
I'm happy to announce that sign-ups for my new olympiad style contest, the United States Ersatz Math Olympiad (USEMO), are open now! The webpage for the USEMO is https://web.evanchen.cc/usemo.html (where sign-ups are posted). The US Ersatz Math Olympiad is a proof-based competition open to all US middle and high school students. Like many competitions, its… Continue reading USEMO sign-ups are open
Circular optimization
This post will mostly be focused on construction-type problems in which you're asked to construct something satisfying property $latex {P}&fg=000000$. Minor spoilers for USAMO 2011/4, IMO 2014/5. 1. What is a leap of faith? Usually, a good thing to do whenever you can is to make ``safe moves'' which are implied by the property $latex… Continue reading Circular optimization
MOHS hardness scale
There's a new addition to my olympiad problems and solutions archive: I created an index of many past IMO/USAMO/USA TST(ST) problems by what my opinions on their difficulties are. You can grab the direct link to the file below: https://evanchen.cc/upload/MOHS-hardness.pdf In short, the scale runs from 0M to 50M in increments of 5M, and every… Continue reading MOHS hardness scale
IMO 2019 Aftermath
Here is my commentary for the 2019 International Math Olympiad, consisting of pictures and some political statements about the problem. Summary This year's USA delegation consisted of leader Po-Shen Loh and deputy leader Yang Liu. The USA scored 227 points, tying for first place with China. For context, that is missing a total of four… Continue reading IMO 2019 Aftermath
Power Overwhelming 