Exploring Euclidean Geometry

Summer AMC Class

The Summer AMC Team, consisting of Dennis Chen (dchenmathcounts), Alex Zheng (molocyxu), William Dai (innumerateguy), Ethan Han (youyanli), Depsilon0, mathgirl199, skyscraper, and Radio2 would like to present their 2020 AMC class, run under the Youth Euclid Association.

Our team consists of a qualifier for the 2020 USAJMO, two three-time AIME qualifiers, and everyone in the team has qualified for the AIME.

Dennis Chen (dchenmathcounts)

Dennis Chen is a rising sophomore in the Bay Area. He has qualified for the AIME as an 8th and 9th grader and has achieved a score of 121.5 on the AMC 10B, receiving the Distinguished Honor Roll, and he has qualified for the USAJMO as a 9th grader with a score of 11 on the AIME I.

His works include Proofs in Competition Math: Volume 1 and Volume 2, written with Alex Toller and Freya Edholm and Exploring Euclidean Geometry, Version 2. He also runs the MAST Program for AIME qualifiers looking to improve their score on computational exams.

He runs cross-country and track, enjoys watching psychological thrillers, reading manga, and playing games.

William Dai (innumerateguy)

William Dai is a rising sophomore who has been active in competition math for the past four years. He has previously made AIME three times, competed in Texas MATHCOUNTS State, was on the 2019 Texas C PuMAC team, and participated in many other mathematics contests. This current year, he made AMC 10A DHR with a score of 136.5 and scored 9 on AIME I. His favorite subject of contest math is combinatorics and he particularly likes elegant recursions.

Aside from contest math, William also has an interest in competitive programming and has made USACO Silver. He also participates in Codeforces contests. In his free time, he likes reading short stories and listening to piano music.

Ethan Han (youyanli)

Ethan Han will be a freshman in the coming school year. He qualified for both the 2019 and 2020 AIMEs and helped teach AMC 10 classes at the YEA during the school year. He enjoys eating Asian food and listening to classical music as well as learning and doing math.

Alex Zheng (molocyxu)

molocyxu is a rising freshman and is a member of the AoPS community hoping to help new students learn more about competitive math. Throughout middle school, molocyxu has participated in many mathematics competitions, including the AMCs, AIME, HMMT, ARML, and more. Outside of math, he enjoys solving puzzles, playing Tetris, and spending too much time on Discord.


Depsilon0 is a rising sophomore who lives in the Bay Area. He has made AIME 3 times as a 7th, 8th, and 9th grader, and has achieved scores of 120 on the AMC 12 and 10 on this year's AIME II (AOIME). Depsilon0 has also taken a significant number of advanced math courses, including multivariable calculus, linear algebra, differential equations, and (most recently) real/complex analysis. Outside of math, he also enjoys physics, chemistry, and swimming.


mathgirl199 is a rising 8th grader. She took the AMC 10 this year, qualifying for AIME and making the Achievement Roll and she received a score of 9 on this year's AIME II (AOIME). In her free time she likes to read.


Radio2 is a USAMTS Perfect Scorer and a rising freshman at the University of Oxford. He enjoys sudoku, Minesweeper, and Latin in his free time, and his ambition is to document all future Reaper games.


skyscraper is a rising freshman that has qualified for the AIME in middle school, and is teaching at the YEA Summer AMC 10 Course this year. He enjoys reading manga and writing problems in his spare time. (Stay tuned for the July Mathematics Competitions!)

  1. The YEA is a registered 501(c)(3) non-profit organization.
  2. The students involved in running this program will not earn a single cent from it.

You may find the signup link here.

Course Overview

We will be running a 4-week program with two lessons a week, handouts to read beforehand for each lesson, and problem sets to submit as homework after each lesson. This will be an intensive course, so we do not recommend students already significantly busy in the summer to sign up for this program as well.

Each lesson will be 75 minutes. A large portion of the learning will be self-guided and depend on each student’s effort on handouts and problem sets. Our philosophy is to create a program that will continue to be useful even after the class is over, so the class will be designed to promote good study habits and self-sufficiency, encourage students to ask for help when they need it, and show the scope of math competitions. To this end, we provide lists of further reading to peruse in each handout. In addition, solutions to problems on problem sets will be submitted to teachers and graded with some comments.

Here is an overview of the lessons. The fifth lesson will be the hardest, so we will request that students do special things to prepare for it a week before.

Lesson Subject
1 Algebra - Manipulations
2 Counting - Basics
3 Counting - Perspectives
4 Geometry - Angle Chasing
5 Geometry - Lengths and Areas in Triangles
6 3D Geometry
7 GCD and LCM
8 Modular Arithmetic


Classes will be on Mondays and Thursdays, from 1:45-3:00 PM PDT. The class will begin on July 6th.

Here are the local times for all USA timezones. Arizona does not observe daylight savings, so the class will be at 1:45-3:00 PM in their timezone. International students should consult a timezone converter to see when the class is in their local time.

Timezone Local Time
PDT 1:45-3:00 PM
MDT 2:45-4:00 PM
CDT 3:45-5:00 PM
EDT 4:45-6:00 PM


Classes for “Pedagogy” and “Mistakes” will be open to the public, with the former occurring before the first lesson and the latter after the last lesson. We will also be hosting a mock AMC 10 written by the team as a final exam, which will also be posted in the Mock Contests forum.

Pedagogy is scheduled for June 28th, from 1:45-3:00 PM in PDT. (Refer to the timetable to see what time that is in your timezone.) Pedagogy will discuss learning how to learn, some takeaways from math competitions, resource recommendations, and will also have a few problems. This is a lecture for the general public, so parents are encouraged to attend as well. The problems will be on the easy side for accessibility.

Mistakes will be about minimizing silly mistakes (“sillies”) in math competitions. We will present some questions where it's easy to make a mistake, go over how to reduce making these mistakes, and talk about the best way to deal with making silly mistakes after a contest.

Pedagogy Details

We will be sending out the zoom information on google classroom. If you're interested, please join the Google Classroom with the code xj7gpqc, where we will announce the zoom meeting information. Signups are not binding. We will also be releasing further samples and will answer questions asked there.

More Details

There are several official materials our team has created regarding policy and procedure for this class. These are the official syllabus and course overview.

Certain internal details, such as how grading works and how communication will work, will be revealed to students and parents who signed up in due time.


The class will cost 100 dollars. Please send the money via PayPal to the Youth Euclid Association at


and make sure you send the payment as a friend. Please include the student's name and specify that the payment is for the YEA 2020 Summer AMC Class. In the transaction notes, please include the student's name and specify that the payment is for the YEA 2020 Summer AMC Class.

You may drop the class anytime before the second lesson for a full refund. The payment must be made in full before the first lesson.


If you have any questions, send an email to both of these addresses: