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k a April Highlights and 2025 AoPS Online Class Information
jlacosta   0
Apr 2, 2025
Spring is in full swing and summer is right around the corner, what are your plans? At AoPS Online our schedule has new classes starting now through July, so be sure to keep your skills sharp and be prepared for the Fall school year! Check out the schedule of upcoming classes below.

WOOT early bird pricing is in effect, don’t miss out! If you took MathWOOT Level 2 last year, no worries, it is all new problems this year! Our Worldwide Online Olympiad Training program is for high school level competitors. AoPS designed these courses to help our top students get the deep focus they need to succeed in their specific competition goals. Check out the details at this link for all our WOOT programs in math, computer science, chemistry, and physics.

Looking for summer camps in math and language arts? Be sure to check out the video-based summer camps offered at the Virtual Campus that are 2- to 4-weeks in duration. There are middle and high school competition math camps as well as Math Beasts camps that review key topics coupled with fun explorations covering areas such as graph theory (Math Beasts Camp 6), cryptography (Math Beasts Camp 7-8), and topology (Math Beasts Camp 8-9)!

Be sure to mark your calendars for the following events:
[list][*]April 3rd (Webinar), 4pm PT/7:00pm ET, Learning with AoPS: Perspectives from a Parent, Math Camp Instructor, and University Professor
[*]April 8th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MATHCOUNTS State Discussion
April 9th (Webinar), 4:00pm PT/7:00pm ET, Learn about Video-based Summer Camps at the Virtual Campus
[*]April 10th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MathILy and MathILy-Er Math Jam: Multibackwards Numbers
[*]April 22nd (Webinar), 4:00pm PT/7:00pm ET, Competitive Programming at AoPS (USACO).[/list]
Our full course list for upcoming classes is below:
All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.

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0 replies
jlacosta
Apr 2, 2025
0 replies
k i Suggestion Form
jwelsh   0
May 6, 2021
Hello!

Given the number of suggestions we’ve been receiving, we’re transitioning to a suggestion form. If you have a suggestion for the AoPS website, please submit the Google Form:
Suggestion Form

To keep all new suggestions together, any new suggestion threads posted will be deleted.

Please remember that if you find a bug outside of FTW! (after refreshing to make sure it’s not a glitch), make sure you’re following the How to write a bug report instructions and using the proper format to report the bug.

Please check the FTW! thread for bugs and post any new ones in the For the Win! and Other Games Support Forum.
0 replies
jwelsh
May 6, 2021
0 replies
k i Read me first / How to write a bug report
slester   3
N May 4, 2019 by LauraZed
Greetings, AoPS users!

If you're reading this post, that means you've come across some kind of bug, error, or misbehavior, which nobody likes! To help us developers solve the problem as quickly as possible, we need enough information to understand what happened. Following these guidelines will help us squash those bugs more effectively.

Before submitting a bug report, please confirm the issue exists in other browsers or other computers if you have access to them.

For a list of many common questions and issues, please see our user created FAQ, Community FAQ, or For the Win! FAQ.

What is a bug?
A bug is a misbehavior that is reproducible. If a refresh makes it go away 100% of the time, then it isn't a bug, but rather a glitch. That's when your browser has some strange file cached, or for some reason doesn't render the page like it should. Please don't report glitches, since we generally cannot fix them. A glitch that happens more than a few times, though, could be an intermittent bug.

If something is wrong in the wiki, you can change it! The AoPS Wiki is user-editable, and it may be defaced from time to time. You can revert these changes yourself, but if you notice a particular user defacing the wiki, please let an admin know.

The subject
The subject line should explain as clearly as possible what went wrong.

Bad: Forum doesn't work
Good: Switching between threads quickly shows blank page.

The report
Use this format to report bugs. Be as specific as possible. If you don't know the answer exactly, give us as much information as you know. Attaching a screenshot is helpful if you can take one.

Summary of the problem:
Page URL:
Steps to reproduce:
1.
2.
3.
...
Expected behavior:
Frequency:
Operating system(s):
Browser(s), including version:
Additional information:


If your computer or tablet is school issued, please indicate this under Additional information.

Example
Summary of the problem: When I click back and forth between two threads in the site support section, the content of the threads no longer show up. (See attached screenshot.)
Page URL: http://artofproblemsolving.com/community/c10_site_support
Steps to reproduce:
1. Go to the Site Support forum.
2. Click on any thread.
3. Click quickly on a different thread.
Expected behavior: To see the second thread.
Frequency: Every time
Operating system: Mac OS X
Browser: Chrome and Firefox
Additional information: Only happens in the Site Support forum. My tablet is school issued, but I have the problem at both school and home.

How to take a screenshot
Mac OS X: If you type ⌘+Shift+4, you'll get a "crosshairs" that lets you take a custom screenshot size. Just click and drag to select the area you want to take a picture of. If you type ⌘+Shift+4+space, you can take a screenshot of a specific window. All screenshots will show up on your desktop.

Windows: Hit the Windows logo key+PrtScn, and a screenshot of your entire screen. Alternatively, you can hit Alt+PrtScn to take a screenshot of the currently selected window. All screenshots are saved to the Pictures → Screenshots folder.

Advanced
If you're a bit more comfortable with how browsers work, you can also show us what happens in the JavaScript console.

In Chrome, type CTRL+Shift+J (Windows, Linux) or ⌘+Option+J (Mac).
In Firefox, type CTRL+Shift+K (Windows, Linux) or ⌘+Option+K (Mac).
In Internet Explorer, it's the F12 key.
In Safari, first enable the Develop menu: Preferences → Advanced, click "Show Develop menu in menu bar." Then either go to Develop → Show Error console or type Option+⌘+C.

It'll look something like this:
IMAGE
3 replies
slester
Apr 9, 2015
LauraZed
May 4, 2019
k i Community Safety
dcouchman   0
Jan 18, 2018
If you find content on the AoPS Community that makes you concerned for a user's health or safety, please alert AoPS Administrators using the report button (Z) or by emailing sheriff@aops.com . You should provide a description of the content and a link in your message. If it's an emergency, call 911 or whatever the local emergency services are in your country.

Please also use those steps to alert us if bullying behavior is being directed at you or another user. Content that is "unlawful, harmful, threatening, abusive, harassing, tortuous, defamatory, vulgar, obscene, libelous, invasive of another's privacy, hateful, or racially, ethnically or otherwise objectionable" (AoPS Terms of Service 5.d) or that otherwise bullies people is not tolerated on AoPS, and accounts that post such content may be terminated or suspended.
0 replies
dcouchman
Jan 18, 2018
0 replies
Arbitrary point on BC and its relation with orthocenter
falantrng   28
N 11 minutes ago by Z4ADies
Source: Balkan MO 2025 P2
In an acute-angled triangle \(ABC\), \(H\) be the orthocenter of it and \(D\) be any point on the side \(BC\). The points \(E, F\) are on the segments \(AB, AC\), respectively, such that the points \(A, B, D, F\) and \(A, C, D, E\) are cyclic. The segments \(BF\) and \(CE\) intersect at \(P.\) \(L\) is a point on \(HA\) such that \(LC\) is tangent to the circumcircle of triangle \(PBC\) at \(C.\) \(BH\) and \(CP\) intersect at \(X\). Prove that the points \(D, X, \) and \(L\) lie on the same line.

Proposed by Theoklitos Parayiou, Cyprus
28 replies
1 viewing
falantrng
Apr 27, 2025
Z4ADies
11 minutes ago
more incircles and tangents
rmtf1111   83
N 25 minutes ago by math-olympiad-clown
Source: EGMO 2019 P4
Let $ABC$ be a triangle with incentre $I$. The circle through $B$ tangent to $AI$ at $I$ meets side $AB$ again at $P$. The circle through $C$ tangent to $AI$ at $I$ meets side $AC$ again at $Q$. Prove that $PQ$ is tangent to the incircle of $ABC.$
83 replies
rmtf1111
Apr 10, 2019
math-olympiad-clown
25 minutes ago
Cardinality of sets containing both multiples and non-multiples of 3
tom-nowy   1
N 37 minutes ago by Tkn
Source: Own
Let $n$ be a positive integer, and let $N$ be the set $\{ 1,2, \ldots, n\}$.
Let the sets $X_n$ and $Y_n$ be difined as:
\begin{align*}
X_n = &\left\{ (x_1,x_2,x_3) \in N^3  \mid  x_1+x_2+x_3 \text{ is not divisible by } 3. \right\}, \\
Y_n = &\left\{ (y_1,y_2,y_3) \in  N^3  \mid  \text{Among }  y_1-y_2,\, y_2-y_3,\, y_3-y_1, 
\text{ at least one is} \right. \\ 
& \left. \text{\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:divisible by }  3  \text{ and at least one is not divisible by } 3. \right\}. 
\end{align*}Which is larger, $\left| X_n \right|$ or $\left| Y_n \right|$ ?
1 reply
tom-nowy
3 hours ago
Tkn
37 minutes ago
Constant sum
M4RI0   3
N 38 minutes ago by Rohit-2006
Source: Cono Sur Olympiad, Uruguay 1989, Problem #5
Let $ABCD$ be a square with diagonals $AC$ and $BD$, and $P$ a point in one of the sides of the square. Show that the sum of the distances from P to the diagonals is constant.
3 replies
M4RI0
May 14, 2006
Rohit-2006
38 minutes ago
This has been going on for a while now, can anyone else relate?
jmr2010   2
N Yesterday at 3:02 AM by valisaxieamc
Most of the time when I type in something for the tags or search for a user, the AoPS suggestion box pops up, and most of the time, when I click the suggestion, the box just disappears, meaning the automatic system usually never works
2 replies
jmr2010
Tuesday at 7:16 PM
valisaxieamc
Yesterday at 3:02 AM
Cannot post PHP
char0221   2
N Yesterday at 2:01 AM by bpan2021
Summary of the problem: If I try to post anything with PHP (a coding language), it
Page URL: In any forum or private messages
Steps to reproduce:
1. Create a post.
2. Put some PHP inside, can't give example
Expected behavior: Should post the message
Frequency: 100%
Operating system(s): macOS Sequoia 15.2.1
Browser(s), including version: Safari
Additional information: See attachments
2 replies
char0221
Yesterday at 1:23 AM
bpan2021
Yesterday at 2:01 AM
k How to remove tags from a PM after you've removed yourself from it
Platinum_Dragon   2
N Tuesday at 7:32 PM by Platinum_Dragon
Is it possible? Because it's kind of annoying to have a whole bunch of tags that stick around forever.

thank you
2 replies
Platinum_Dragon
Tuesday at 7:25 PM
Platinum_Dragon
Tuesday at 7:32 PM
k Reaper....
Happycat2   22
N Tuesday at 6:51 PM by jlacosta
Can someone explain what the reaper is this time? I'm sorry but I don't know what "Rapper ear error a pear perrier ear ape ea games" means.
22 replies
Happycat2
Apr 27, 2025
jlacosta
Tuesday at 6:51 PM
k Reaper Description
Jwenslawski   1
N Tuesday at 6:24 PM by LostInBali
What does the Reaper game description mean?

"rapper eaE error a Sear perriTr ear apeIea games"

Is it in another language?
1 reply
Jwenslawski
Tuesday at 5:07 PM
LostInBali
Tuesday at 6:24 PM
k blog glitch?
ngelyy   18
N Apr 29, 2025 by Blossom_tree_17
RESOLVED
18 replies
ngelyy
Apr 29, 2025
Blossom_tree_17
Apr 29, 2025
k Hieroglyph (and Petroglyph?) on Post #1
awesomeming327.   10
N Apr 28, 2025 by bpan2021
Steps to Reproduce:
1. Click this link
2. Scroll up.
Behavior: it should show two copies of a certain "post #0" above post #1.
Frequency: 100%

Mac OS, Arc Browser (which runs on Chromium)

Note: you can also click on "view topic" on the N7 of the 2023 ISL
10 replies
awesomeming327.
Apr 27, 2025
bpan2021
Apr 28, 2025
k something glitched?
JohannIsBach   10
N Apr 27, 2025 by valisaxieamc
hi. my aops whenever i go 2 the website the website is like way to big and i cant access anything? i am on via an ingognito window but its kind of inconvenient not sure if its just my laptop or the website. i cant recreat it on any other device? plz help [/resolved]
10 replies
JohannIsBach
Apr 25, 2025
valisaxieamc
Apr 27, 2025
k alcumus not working? [RESOLVED]
JohannIsBach   3
N Apr 27, 2025 by MathDolphin95
4 some reason alcumus isnt working??? in the 1st attachment there isnt any "play, profile, ...etc."
and in the second pic i clicked the "play" button, but its just a blank screen??? i tried refreshing it didnt work????
3 replies
JohannIsBach
Apr 27, 2025
MathDolphin95
Apr 27, 2025
Is this just my device? Typing glitch
pearlhaas   4
N Apr 26, 2025 by valisaxieamc
This started today.
When I tried to type in the AoPS homework section (as well as forums), where you put your answers into the slots, I found that I couldn’t? This might only be my device but it was delaying my work and I just thought I’d share.
I refreshed multiple times, but it only works sometimes.
Sometimes, the blinking blue bar shows but I can’t type, and other times, the blue bar doesn’t show at all.
I am able to type this forum up since this was one of the few times that my device let me type (for more, I have an iPad. Not sure what generation, but it’s a pretty recent version, I believe).
If this is a problem with my device, I apologize for wasting your time :)
Just wanted to make sure I could get this notice out if others have the same problem.
4 replies
pearlhaas
Apr 25, 2025
valisaxieamc
Apr 26, 2025
Tiling problem (Combinatorics or Number Theory?)
Rukevwe   4
N Yesterday at 3:26 AM by CrazyInMath
Source: 2022 Nigerian MO Round 3/Problem 3
A unit square is removed from the corner of an $n \times n$ grid, where $n \geq 2$. Prove that the remainder can be covered by copies of the figures of $3$ or $5$ unit squares depicted in the drawing below.
IMAGE

Note: Every square must be covered once and figures must not go over the bounds of the grid.
4 replies
Rukevwe
May 2, 2022
CrazyInMath
Yesterday at 3:26 AM
Tiling problem (Combinatorics or Number Theory?)
G H J
Source: 2022 Nigerian MO Round 3/Problem 3
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Rukevwe
288 posts
#1 • 1 Y
Y by ImSh95
A unit square is removed from the corner of an $n \times n$ grid, where $n \geq 2$. Prove that the remainder can be covered by copies of the figures of $3$ or $5$ unit squares depicted in the drawing below.
[asy]
import geometry;

draw((-1.5,0)--(-3.5,0)--(-3.5,2)--(-2.5,2)--(-2.5,1)--(-1.5,1)--cycle);
draw((-3.5,1)--(-2.5,1)--(-2.5,0));

draw((0.5,0)--(0.5,3)--(1.5,3)--(1.5,1)--(3.5,1)--(3.5,0)--cycle);
draw((1.5,0)--(1.5,1));
draw((2.5,0)--(2.5,1));
draw((0.5,1)--(1.5,1));
draw((0.5,2)--(1.5,2));
[/asy]

Note: Every square must be covered once and figures must not go over the bounds of the grid.
This post has been edited 2 times. Last edited by Rukevwe, May 6, 2022, 2:54 PM
Z K Y
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ZhuTao
37 posts
#2 • 3 Y
Y by VZH, ImSh95, Rukevwe
Maybe combinatorics.
Use induction. Two 3-unit figure can make a $2\times 3$ rectangular, so $2xy$ 3-unit figure can make $2x\times 3y$ rectangular.
Assume cases when $2\leq n \leq k$ have been proved. Then when $n=k+1$, try rewrite $n=2x+1+3y$. If such $(x,y)\in \mathbb{Z}_{>0}^2$ exists, $(k+1)\times(k+1)$ with a unit removed from a corner can be made as below.

https://i.postimg.cc/rFCBdRXS/Tiling-Problem-1.jpg

And when $n = 6$ or $n\geq 8$, such $(x,y)$ does exist. So we only need to prove when$n=2,3,4,5,7$.
$n=2,3$ is trivial.
$n=4$: https://i.postimg.cc/DwSP9Rg8/Tiling-Problem-2.jpg
$n=5$: https://i.postimg.cc/ZKB94mGt/Tiling-Problem-3.jpg
$n=7$: https://i.postimg.cc/J0JG3cc7/Tiling-Problem-4.jpg
Z K Y
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oVlad
1742 posts
#3 • 3 Y
Y by ImSh95, Mango247, Mango247
This was originally a problem from the Estonian Mathematical Olympiad 2009. It was also later on used as Problem 4 in the Junior Mathematical Danube Competition 2016. (Edit: feel free to copy the asy code from the linked post for a better diagram)
This post has been edited 1 time. Last edited by oVlad, May 3, 2022, 2:02 PM
Z K Y
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Rukevwe
288 posts
#4
Y by
Click to reveal hidden text
Beautiful solution
Z K Y
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CrazyInMath
457 posts
#5
Y by
sketch, as I can't put pictures
Z K Y
N Quick Reply
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