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k a May Highlights and 2025 AoPS Online Class Information
jlacosta   0
May 1, 2025
May is an exciting month! National MATHCOUNTS is the second week of May in Washington D.C. and our Founder, Richard Rusczyk will be presenting a seminar, Preparing Strong Math Students for College and Careers, on May 11th.

Are you interested in working towards MATHCOUNTS and don’t know where to start? We have you covered! If you have taken Prealgebra, then you are ready for MATHCOUNTS/AMC 8 Basics. Already aiming for State or National MATHCOUNTS and harder AMC 8 problems? Then our MATHCOUNTS/AMC 8 Advanced course is for you.

Summer camps are starting next month at the Virtual Campus in math and language arts that are 2 - to 4 - weeks in duration. Spaces are still available - don’t miss your chance to have an enriching summer experience. 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 upcoming events:
[list][*]May 9th, 4:30pm PT/7:30pm ET, Casework 2: Overwhelming Evidence — A Text Adventure, a game where participants will work together to navigate the map, solve puzzles, and win! All are welcome.
[*]May 19th, 4:30pm PT/7:30pm ET, What's Next After Beast Academy?, designed for students finishing Beast Academy and ready for Prealgebra 1.
[*]May 20th, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 1 Math Jam, Problems 1 to 4, join the Canada/USA Mathcamp staff for this exciting Math Jam, where they discuss solutions to Problems 1 to 4 of the 2025 Mathcamp Qualifying Quiz!
[*]May 21st, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 2 Math Jam, Problems 5 and 6, Canada/USA Mathcamp staff will discuss solutions to Problems 5 and 6 of the 2025 Mathcamp Qualifying Quiz![/list]
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0 replies
jlacosta
May 1, 2025
0 replies
k i Adding contests to the Contest Collections
dcouchman   1
N Apr 5, 2023 by v_Enhance
Want to help AoPS remain a valuable Olympiad resource? Help us add contests to AoPS's Contest Collections.

Find instructions and a list of contests to add here: https://artofproblemsolving.com/community/c40244h1064480_contests_to_add
1 reply
dcouchman
Sep 9, 2019
v_Enhance
Apr 5, 2023
k i Zero tolerance
ZetaX   49
N May 4, 2019 by NoDealsHere
Source: Use your common sense! (enough is enough)
Some users don't want to learn, some other simply ignore advises.
But please follow the following guideline:


To make it short: ALWAYS USE YOUR COMMON SENSE IF POSTING!
If you don't have common sense, don't post.


More specifically:

For new threads:


a) Good, meaningful title:
The title has to say what the problem is about in best way possible.
If that title occured already, it's definitely bad. And contest names aren't good either.
That's in fact a requirement for being able to search old problems.

Examples:
Bad titles:
- "Hard"/"Medium"/"Easy" (if you find it so cool how hard/easy it is, tell it in the post and use a title that tells us the problem)
- "Number Theory" (hey guy, guess why this forum's named that way¿ and is it the only such problem on earth¿)
- "Fibonacci" (there are millions of Fibonacci problems out there, all posted and named the same...)
- "Chinese TST 2003" (does this say anything about the problem¿)
Good titles:
- "On divisors of a³+2b³+4c³-6abc"
- "Number of solutions to x²+y²=6z²"
- "Fibonacci numbers are never squares"


b) Use search function:
Before posting a "new" problem spend at least two, better five, minutes to look if this problem was posted before. If it was, don't repost it. If you have anything important to say on topic, post it in one of the older threads.
If the thread is locked cause of this, use search function.

Update (by Amir Hossein). The best way to search for two keywords in AoPS is to input
[code]+"first keyword" +"second keyword"[/code]
so that any post containing both strings "first word" and "second form".


c) Good problem statement:
Some recent really bad post was:
[quote]$lim_{n\to 1}^{+\infty}\frac{1}{n}-lnn$[/quote]
It contains no question and no answer.
If you do this, too, you are on the best way to get your thread deleted. Write everything clearly, define where your variables come from (and define the "natural" numbers if used). Additionally read your post at least twice before submitting. After you sent it, read it again and use the Edit-Button if necessary to correct errors.


For answers to already existing threads:


d) Of any interest and with content:
Don't post things that are more trivial than completely obvious. For example, if the question is to solve $x^{3}+y^{3}=z^{3}$, do not answer with "$x=y=z=0$ is a solution" only. Either you post any kind of proof or at least something unexpected (like "$x=1337, y=481, z=42$ is the smallest solution). Someone that does not see that $x=y=z=0$ is a solution of the above without your post is completely wrong here, this is an IMO-level forum.
Similar, posting "I have solved this problem" but not posting anything else is not welcome; it even looks that you just want to show off what a genius you are.

e) Well written and checked answers:
Like c) for new threads, check your solutions at least twice for mistakes. And after sending, read it again and use the Edit-Button if necessary to correct errors.



To repeat it: ALWAYS USE YOUR COMMON SENSE IF POSTING!


Everything definitely out of range of common sense will be locked or deleted (exept for new users having less than about 42 posts, they are newbies and need/get some time to learn).

The above rules will be applied from next monday (5. march of 2007).
Feel free to discuss on this here.
49 replies
ZetaX
Feb 27, 2007
NoDealsHere
May 4, 2019
Geometry
AlexCenteno2007   1
N an hour ago by MathLuis
Source: NCA
Let ABC be an acute triangle. The altitudes from B and C intersect the sides AC and AB at E and F, respectively. The internal bisector of ∠A intersects BE and CF at T and S, respectively. The circles with diameters AT and AS intersect the circumcircle of ABC at X and Y, respectively. Prove that XY, EF, and BC meet at the exsimilicenter of BTX and CSY
1 reply
AlexCenteno2007
Today at 4:42 AM
MathLuis
an hour ago
D1032 : A general result on polynomial 2
Dattier   2
N an hour ago by cmjun1109
Source: les dattes à Dattier
Let $P \in \mathbb Q[x,y]$ with $\max(\deg_x(P),\deg_y(P)) \leq d$ and $\forall (a,b) \in \mathbb Z^2 \cap [0,d]^2, P(a,b) \in \mathbb Z$.

Is it true that $\forall (a,b) \in\mathbb Z^2, P(a,b) \in \mathbb Z$?
2 replies
Dattier
Yesterday at 5:19 PM
cmjun1109
an hour ago
Minimal number of divisors
Garfield   7
N an hour ago by Omerking
Source: Serbian junior TST 2nd
Find minimal number of divisors that can number $|2016^m-36^n|$ have,where $m$ and $n$ are natural numbers.
7 replies
Garfield
May 21, 2016
Omerking
an hour ago
geometry problem
kjhgyuio   1
N an hour ago by Mathzeus1024
........
1 reply
kjhgyuio
May 11, 2025
Mathzeus1024
an hour ago
Geometry
MathsII-enjoy   0
an hour ago
Given triangle $ABC$ inscribed in $(O)$ with $M$ being the midpoint of $BC$. The tangents at $B, C$ of $(O)$ intersect at $D$. Let $N$ be the projection of $O$ onto $AD$. On the perpendicular bisector of $BC$, take a point $K$ that is not on $(O)$ and different from M. Circle $(KBC)$ intersects $AK$ at $F$. Lines $NF$ and $AM$ intersect at $E$. Prove that $AEF$ is an isosceles triangle.
0 replies
MathsII-enjoy
an hour ago
0 replies
Weird n-variable extremum problem
pithon_with_an_i   1
N an hour ago by Quantum-Phantom
Source: Revenge JOM 2025 Problem 3, Revenge JOMSL 2025 A4
Let $n$ be a positive integer greater or equal to $2$ and let $a_1$, $a_2$, ..., $a_n$ be a sequence of non-negative real numbers. Find the maximum value of $3(a_1  + a_2 + \cdots + a_n) - (a_1^2 + a_2^2 + \cdots + a_n^2) - a_1a_2  \cdots a_n$ in terms of $n$.

(Proposed by Cheng You Seng)
1 reply
pithon_with_an_i
Yesterday at 1:26 PM
Quantum-Phantom
an hour ago
mods with a twist
sketchydealer05   9
N 2 hours ago by lakshya2009
Source: EGMO 2023/5
We are given a positive integer $s \ge 2$. For each positive integer $k$, we define its twist $k’$ as follows: write $k$ as $as+b$, where $a, b$ are non-negative integers and $b < s$, then $k’ = bs+a$. For the positive integer $n$, consider the infinite sequence $d_1, d_2, \dots$ where $d_1=n$ and $d_{i+1}$ is the twist of $d_i$ for each positive integer $i$.
Prove that this sequence contains $1$ if and only if the remainder when $n$ is divided by $s^2-1$ is either $1$ or $s$.
9 replies
sketchydealer05
Apr 16, 2023
lakshya2009
2 hours ago
Ah, easy one
irregular22104   1
N 2 hours ago by alexheinis
Source: Own
In the number series $1,9,9,9,8,...,$ every next number (from the fifth number) is the unit number of the sum of the four numbers preceding it. Is there any cases that we get the numbers $1234$ and $5678$ in this series?
1 reply
irregular22104
Yesterday at 4:01 PM
alexheinis
2 hours ago
Three concurrent circles
jayme   4
N 3 hours ago by jayme
Source: own?
Dear Mathlinkers,

1. ABC a triangle
2. 0 the circumcircle
3. Tb, Tc the tangents to 0 wrt. B, C
4. D the point of intersection of Tb and Tc
5. B', C' the symmetrics of B, C wrt AC, AB
6. 1b, 1c the circumcircles of the triangles BB'D, CC'D.

Prove : 1b, 1c and 0 are concurrents.

Sincerely
Jean-Louis
4 replies
jayme
Yesterday at 3:08 PM
jayme
3 hours ago
angle relations in a convex ABCD given, double segment wanted
parmenides51   12
N 3 hours ago by Nuran2010
Source: Iranian Geometry Olympiad 2018 IGO Intermediate p2
In convex quadrilateral $ABCD$, the diagonals $AC$ and $BD$ meet at the point $P$. We know that $\angle DAC = 90^o$ and $2 \angle ADB = \angle ACB$. If we have $ \angle DBC + 2 \angle ADC = 180^o$ prove that $2AP = BP$.

Proposed by Iman Maghsoudi
12 replies
parmenides51
Sep 19, 2018
Nuran2010
3 hours ago
2021 SMT Guts Round 5 p17-20 - Stanford Math Tournament
parmenides51   5
N 4 hours ago by MATHS_ENTUSIAST
p17. Let the roots of the polynomial $f(x) = 3x^3 + 2x^2 + x + 8 = 0$ be $p, q$, and $r$. What is the sum $\frac{1}{p} +\frac{1}{q} +\frac{1}{r}$ ?


p18. Two students are playing a game. They take a deck of five cards numbered $1$ through $5$, shuffle them, and then place them in a stack facedown, turning over the top card next to the stack. They then take turns either drawing the card at the top of the stack into their hand, showing the drawn card to the other player, or drawing the card that is faceup, replacing it with the card on the top of the pile. This is repeated until all cards are drawn, and the player with the largest sum for their cards wins. What is the probability that the player who goes second wins, assuming optimal play?


p19. Compute the sum of all primes $p$ such that $2^p + p^2$ is also prime.


p20. In how many ways can one color the $8$ vertices of an octagon each red, black, and white, such that no two adjacent sides are the same color?


PS. You should use hide for answers. Collected here.
5 replies
parmenides51
Feb 11, 2022
MATHS_ENTUSIAST
4 hours ago
k Interesting functional equation
IvanRogers1   9
N Today at 5:51 AM by jasperE3
Find all functions $f:  \mathbb{R} \to  \mathbb{R}$ such that $f(x + y) + f(xy) + 1 = f(x) + f(y) + f(xy + 1) \forall x ,y \in \mathbb R$.
9 replies
IvanRogers1
Yesterday at 3:19 PM
jasperE3
Today at 5:51 AM
Assam Mathematics Olympiad 2023 Category III Q16
SomeonecoolLovesMaths   3
N Today at 4:38 AM by nyacide
$n$ is a positive integer such that the product of all its positive divisors is $n^3$. Find all such $n$ less than $100$.
3 replies
1 viewing
SomeonecoolLovesMaths
Sep 11, 2024
nyacide
Today at 4:38 AM
PIE practice
Serengeti22   4
N Today at 1:34 AM by Andyluo
Does anybody know any good problems to practice PIE that range from mid-AMC10/12 level - early AIME level for pracitce.
4 replies
Serengeti22
May 12, 2025
Andyluo
Today at 1:34 AM
angle chasing inside a square, EB = AB (2020 Fall Animath Cup p2)
parmenides51   9
N Nov 21, 2020 by RedFlame2112
Let $ABCD$ be a square and $E$ the point of the segment $[BD]$ such that $EB = AB$. We define the point $F$ as the point of intersection of lines $(CE)$ and $(AD)$. Find the value of the angle $\angle FEA$.
9 replies
parmenides51
Nov 20, 2020
RedFlame2112
Nov 21, 2020
angle chasing inside a square, EB = AB (2020 Fall Animath Cup p2)
G H J
G H BBookmark kLocked kLocked NReply
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parmenides51
30652 posts
#1
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Let $ABCD$ be a square and $E$ the point of the segment $[BD]$ such that $EB = AB$. We define the point $F$ as the point of intersection of lines $(CE)$ and $(AD)$. Find the value of the angle $\angle FEA$.
This post has been edited 1 time. Last edited by parmenides51, Nov 20, 2020, 8:45 PM
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yofro
3151 posts
#2
Y by
Wait what? Isn't $E$ the intersection of the diagonals, making $F=A$, thus the angle is $0$?? Or does $(CE)$ mean something else?
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parmenides51
30652 posts
#3
Y by
$E$ lies only on the one diagonal $BD$ , it says $EB=BA$ and not $EB=BD$
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yofro
3151 posts
#4 • 3 Y
Y by Mango247, Mango247, Mango247
parmenides51 wrote:
$E$ lies only on the one diagonal $BD$ , it says $EB=BA$ and not $EB=BD$

Right, but $E$ as the intersection works, since $EB=AB=\frac{\sqrt2}{2}$ for sq side length $1$.
This post has been edited 1 time. Last edited by yofro, Nov 20, 2020, 9:02 PM
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natmath
8219 posts
#5
Y by
$\angle FEA=180-\angle CEA$
$\angle CEA=\angle AEB+\angle CEB$
Since $\Delta ABE \cong \Delta BCE$, we have $\angle CEA=2\angle AEB$
$\angle AEB=\frac{180-45}{2}$

So $\angle FEA=45$
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natmath
8219 posts
#6
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yofro wrote:
$EB=AB=\frac{\sqrt2}{2}$ for sq side length 1
Why is $AB=\frac{\sqrt2}{2}$?
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yofro
3151 posts
#7
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natmath wrote:
yofro wrote:
$EB=AB=\frac{\sqrt2}{2}$ for sq side length 1
Why is $AB=\frac{\sqrt2}{2}$?

By distance formula...

Ok can someone give a diagram because I'm confused.
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natmath
8219 posts
#8
Y by
https://www.geogebra.org/calculator/h7dexffs
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sunken rock
4394 posts
#9
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Any point $F$ of the arc AC of the circle (B, BA) has this property. Best regards, sunken rock
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RedFlame2112
1445 posts
#10
Y by
isn't the answer
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