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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)!

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[*]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
Jbmo 2011 Problem 4
Eukleidis   13
N 24 minutes ago by Adventure1000
Source: Jbmo 2011
Let $ABCD$ be a convex quadrilateral and points $E$ and $F$ on sides $AB,CD$ such that
\[\tfrac{AB}{AE}=\tfrac{CD}{DF}=n\]

If $S$ is the area of $AEFD$ show that ${S\leq\frac{AB\cdot CD+n(n-1)AD^2+n^2DA\cdot BC}{2n^2}}$
13 replies
Eukleidis
Jun 21, 2011
Adventure1000
24 minutes ago
an algebra question
kjhgyuio   1
N 31 minutes ago by aidan0626
.........
1 reply
kjhgyuio
38 minutes ago
aidan0626
31 minutes ago
we can find one pair of a boy and a girl
orl   16
N an hour ago by ezpotd
Source: Vietnam TST 2001 for the 42th IMO, problem 3
Some club has 42 members. It’s known that among 31 arbitrary club members, we can find one pair of a boy and a girl that they know each other. Show that from club members we can choose 12 pairs of knowing each other boys and girls.
16 replies
orl
Jun 26, 2005
ezpotd
an hour ago
teleporting wizard starts on point (2017, 101), 4 moves
parmenides51   1
N an hour ago by jasperE3
Source: 2018 USAIMEO #2 p5 (Mock AIME -USAJMO) https://artofproblemsolving.com/community/c594864h1572209p9658908
A teleporting wizard starts on the point $(2017, 101)$ and can teleport to other Cartesian coordinates with only $1$ of $4$ moves: $(x, y) \to (x + y, y)$, $(x, y) \to (x - y, y)$ when $x > y$, $(x, y) \to (x, x + y)$, and $(x, y) \to (x, y - x)$ when $y > x$.

(a) Let $P(x)$ be any polynomial with positive integer coefficients that passes through $(0, 0)$. Show that for all such $P(x)$, there exists a unique point on the curve where the wizard can land on.

(b) For each $P(x)$, let $S$ be this unique point. Find the equation of the graph that contains all potential $S$.
1 reply
parmenides51
Nov 17, 2023
jasperE3
an hour ago
Arithmetic Series and Common Differences
4everwise   6
N 5 hours ago by epl1
For each positive integer $k$, let $S_k$ denote the increasing arithmetic sequence of integers whose first term is $1$ and whose common difference is $k$. For example, $S_3$ is the sequence $1,4,7,10,...$. For how many values of $k$ does $S_k$ contain the term $2005$?
6 replies
4everwise
Nov 10, 2005
epl1
5 hours ago
find number of elements in H
Darealzolt   0
6 hours ago
If \( H \) is the set of positive real solutions to the system
\[
x^3 + y^3 + z^3 = x + y + z
\]\[
x^2 + y^2 + z^2 = xyz
\]then find the number of elements in \( H \).
0 replies
Darealzolt
6 hours ago
0 replies
old problem from an open contest
Darealzolt   0
6 hours ago
Given that $a, b \in \mathbb{R}$ satisfy
\[
a + \frac{1}{a + 2015} = b - 4030 + \frac{1}{b - 2015}
\]and $|a - b| > 5000$. Determine the value of
\[
\frac{ab}{2015} - a + b.
\]
0 replies
Darealzolt
6 hours ago
0 replies
f_n(x)=\sum sin(nx)/n
Urumqi   6
N Today at 1:04 AM by Urumqi
$F_n(x)=\sum_{k=1}^{n}\frac{\sin (kx)}{k}$, prove that for all $x \in (0,\pi), F_n(x)>0$.

Thanks.
6 replies
Urumqi
Yesterday at 2:13 AM
Urumqi
Today at 1:04 AM
Looking for users and developers
derekli   9
N Today at 12:57 AM by musicalpenguin
Guys I've been working on a web app that lets you grind high school lvl math. There's AMCs, AIME, BMT, HMMT, SMT etc. Also, it's infinite practice so you can keep grinding without worrying about finding new problems. Please consider helping me out by testing and also consider joining our developer team! :P :blush:

Link: https://stellarlearning.app/competitive
9 replies
derekli
Yesterday at 12:57 AM
musicalpenguin
Today at 12:57 AM
Regular tetrahedron
vanstraelen   6
N Yesterday at 11:36 PM by Math-lover1
Given the points $O(0,0,0),A(1,0,0),B(\frac{1}{2},\frac{\sqrt{3}}{2},0)$
a) Determine the point $C$, above the xy-plane, such that the pyramid $OABC$ is a regular tetrahedron.
b) Calculate the volume.
c) Calculate the radius of the inscribed sphere and the radius of the circumscribed sphere.
6 replies
vanstraelen
Yesterday at 3:23 PM
Math-lover1
Yesterday at 11:36 PM
How many pairs
Ecrin_eren   5
N Yesterday at 10:19 PM by imbadatmath1233


Let n be a natural number and p be a prime number. How many different pairs (n, p) satisfy the equation:

p + 2^p + 3 = n^2 ?



5 replies
Ecrin_eren
May 2, 2025
imbadatmath1233
Yesterday at 10:19 PM
Name of a point on a circle
clarkculus   1
N Yesterday at 10:05 PM by martianrunner
Is there a name for the point $P'$ with respect to a circle $\Gamma$, a diameter $\ell$, and a given point $P$, such that $P'$ is the reflection of the $P$-antipode about $\ell$? Equivalently, $P'$ is the the other intersection of $\Gamma$ and the line through $P$ parallel to $\ell$.
1 reply
clarkculus
Yesterday at 9:45 PM
martianrunner
Yesterday at 10:05 PM
A Collection of Good Problems from my end
SomeonecoolLovesMaths   5
N Yesterday at 8:46 PM by Math-lover1
This is a collection of good problems and my respective attempts to solve them. I would like to encourage everyone to post their solutions to these problems, if any. This will not only help others verify theirs but also perhaps bring forward a different approach to the problem. I will constantly try to update the pool of questions.

The difficulty level of these questions vary from AMC 10 to AIME. (Although the main pool of questions were prepared as a mock test for IOQM over the years)

Problem 1

Problem 2

Problem 3
5 replies
SomeonecoolLovesMaths
Yesterday at 8:16 AM
Math-lover1
Yesterday at 8:46 PM
GCD of consecutive terms
nsato   33
N Yesterday at 7:38 PM by reni_wee
The numbers in the sequence 101, 104, 109, 116, $\dots$ are of the form $a_n = 100 + n^2$, where $n = 1$, 2, 3, $\dots$. For each $n$, let $d_n$ be the greatest common divisor of $a_n$ and $a_{n + 1}$. Find the maximum value of $d_n$ as $n$ ranges through the positive integers.
33 replies
nsato
Mar 14, 2006
reni_wee
Yesterday at 7:38 PM
prove that $\angle Q L A=\angle M L A$
NJAX   3
N Apr 2, 2025 by Baimukh
Source: 2nd Al-Khwarizmi International Junior Mathematical Olympiad 2024, Day2, Problem7
Two circles with centers $O_{1}$ and $O_{2}$ intersect at $P$ and $Q$. Let $\omega$ be the circumcircle of the triangle $P O_{1} O_{2}$; the circle $\omega$ intersect the circles centered at $O_{1}$ and $O_{2}$ at points $A$ and $B$, respectively. The point $Q$ is inside triangle $P A B$ and $P Q$ intersects $\omega$ at $M$. The point $E$ on $\omega$ is such that $P Q=Q E$. Let $M E$ and $A B$ meet at $L$, prove that $\angle Q L A=\angle M L A$.

Proposed by Amir Parsa Hoseini Nayeri, Iran
3 replies
NJAX
May 31, 2024
Baimukh
Apr 2, 2025
prove that $\angle Q L A=\angle M L A$
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G H BBookmark kLocked kLocked NReply
Source: 2nd Al-Khwarizmi International Junior Mathematical Olympiad 2024, Day2, Problem7
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NJAX
29 posts
#1 • 2 Y
Y by GeoKing, Rounak_iitr
Two circles with centers $O_{1}$ and $O_{2}$ intersect at $P$ and $Q$. Let $\omega$ be the circumcircle of the triangle $P O_{1} O_{2}$; the circle $\omega$ intersect the circles centered at $O_{1}$ and $O_{2}$ at points $A$ and $B$, respectively. The point $Q$ is inside triangle $P A B$ and $P Q$ intersects $\omega$ at $M$. The point $E$ on $\omega$ is such that $P Q=Q E$. Let $M E$ and $A B$ meet at $L$, prove that $\angle Q L A=\angle M L A$.

Proposed by Amir Parsa Hoseini Nayeri, Iran
This post has been edited 1 time. Last edited by NJAX, May 31, 2024, 12:34 PM
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v4913
1650 posts
#2 • 1 Y
Y by GeoKing
Since $MP \perp O_1O_2$, $Q$ is the orthocenter of $\triangle{MO_1O_2}$, so $MA = MQ = MB$ and $MQ^2 = ML \cdot ME \implies (LQE)$ is tangent to $MQ$. So, $\angle{QLM} = 2\angle{QPE} = 2\angle{MLA}$.
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sami1618
902 posts
#3 • 1 Y
Y by NJAX
Let $O$ be the circumcenter of $PAB$.

Claim: $Q$ is the incenter of $PAB$
The following equalities are sufficient $$\angle AQP=180^{\circ}-\frac{1}{2}\angle AO_1P=90^{\circ}+\frac{1}{2}\angle ABP$$$$\angle BQP=180^{\circ}-\frac{1}{2}\angle BO_2P=90^{\circ}+\frac{1}{2}\angle BAP$$Claim: $EQOM$ is concyclic
$$\angle QOE=\frac{1}{2}\angle POE=\angle PME$$Claim: $MQ$ is tangent to the circumcircle of $ELQ$
Notice that $MA$ is tangent to the circumcircle of $ELA$ as $\angle MAL=\angle AEM$. Thus $MQ^2=MA^2=ME\cdot ML$.
Claim: $\angle QLA=\angle MLA$
$$2\angle MLB=\angle MOE=\angle MQE=\angle MLQ$$
Attachments:
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Baimukh
9 posts
#4
Y by
Let $Q'$ be the symmetric point of $Q$ relative to $AB$, and $M'$ be the symmetric point of $M$ relative to $AB$. Then $MM' \parallel QQ'$ $\angle QLQ'=\angle MLM'$ $LQ=LQ';$ $LM=LM';$ $ \Longrightarrow \angle LMM'=\angle LM'M=\angle LQQ'=\angle LQ'Q \Longrightarrow \angle QLA=\angle ALQ'=\angle ALM$
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