Stay ahead of learning milestones! Enroll in a class over the summer!

G
Topic
First Poster
Last Poster
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.

Introductory: Grades 5-10

Prealgebra 1 Self-Paced

Prealgebra 1
Sunday, Apr 13 - Aug 10
Tuesday, May 13 - Aug 26
Thursday, May 29 - Sep 11
Sunday, Jun 15 - Oct 12
Monday, Jun 30 - Oct 20
Wednesday, Jul 16 - Oct 29

Prealgebra 2 Self-Paced

Prealgebra 2
Sunday, Apr 13 - Aug 10
Wednesday, May 7 - Aug 20
Monday, Jun 2 - Sep 22
Sunday, Jun 29 - Oct 26
Friday, Jul 25 - Nov 21

Introduction to Algebra A Self-Paced

Introduction to Algebra A
Monday, Apr 7 - Jul 28
Sunday, May 11 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Wednesday, May 14 - Aug 27
Friday, May 30 - Sep 26
Monday, Jun 2 - Sep 22
Sunday, Jun 15 - Oct 12
Thursday, Jun 26 - Oct 9
Tuesday, Jul 15 - Oct 28

Introduction to Counting & Probability Self-Paced

Introduction to Counting & Probability
Wednesday, Apr 16 - Jul 2
Thursday, May 15 - Jul 31
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Wednesday, Jul 9 - Sep 24
Sunday, Jul 27 - Oct 19

Introduction to Number Theory
Thursday, Apr 17 - Jul 3
Friday, May 9 - Aug 1
Wednesday, May 21 - Aug 6
Monday, Jun 9 - Aug 25
Sunday, Jun 15 - Sep 14
Tuesday, Jul 15 - Sep 30

Introduction to Algebra B Self-Paced

Introduction to Algebra B
Wednesday, Apr 16 - Jul 30
Tuesday, May 6 - Aug 19
Wednesday, Jun 4 - Sep 17
Sunday, Jun 22 - Oct 19
Friday, Jul 18 - Nov 14

Introduction to Geometry
Wednesday, Apr 23 - Oct 1
Sunday, May 11 - Nov 9
Tuesday, May 20 - Oct 28
Monday, Jun 16 - Dec 8
Friday, Jun 20 - Jan 9
Sunday, Jun 29 - Jan 11
Monday, Jul 14 - Jan 19

Intermediate: Grades 8-12

Intermediate Algebra
Monday, Apr 21 - Oct 13
Sunday, Jun 1 - Nov 23
Tuesday, Jun 10 - Nov 18
Wednesday, Jun 25 - Dec 10
Sunday, Jul 13 - Jan 18
Thursday, Jul 24 - Jan 22

Intermediate Counting & Probability
Wednesday, May 21 - Sep 17
Sunday, Jun 22 - Nov 2

Intermediate Number Theory
Friday, Apr 11 - Jun 27
Sunday, Jun 1 - Aug 24
Wednesday, Jun 18 - Sep 3

Precalculus
Wednesday, Apr 9 - Sep 3
Friday, May 16 - Oct 24
Sunday, Jun 1 - Nov 9
Monday, Jun 30 - Dec 8

Advanced: Grades 9-12

Olympiad Geometry
Tuesday, Jun 10 - Aug 26

Calculus
Tuesday, May 27 - Nov 11
Wednesday, Jun 25 - Dec 17

Group Theory
Thursday, Jun 12 - Sep 11

Contest Preparation: Grades 6-12

MATHCOUNTS/AMC 8 Basics
Wednesday, Apr 16 - Jul 2
Friday, May 23 - Aug 15
Monday, Jun 2 - Aug 18
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

MATHCOUNTS/AMC 8 Advanced
Friday, Apr 11 - Jun 27
Sunday, May 11 - Aug 10
Tuesday, May 27 - Aug 12
Wednesday, Jun 11 - Aug 27
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

AMC 10 Problem Series
Friday, May 9 - Aug 1
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Tuesday, Jun 17 - Sep 2
Sunday, Jun 22 - Sep 21 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Monday, Jun 23 - Sep 15
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

AMC 10 Final Fives
Sunday, May 11 - Jun 8
Tuesday, May 27 - Jun 17
Monday, Jun 30 - Jul 21

AMC 12 Problem Series
Tuesday, May 27 - Aug 12
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Wednesday, Aug 6 - Oct 22

AMC 12 Final Fives
Sunday, May 18 - Jun 15

F=ma Problem Series
Wednesday, Jun 11 - Aug 27

WOOT Programs
Visit the pages linked for full schedule details for each of these programs!


MathWOOT Level 1
MathWOOT Level 2
ChemWOOT
CodeWOOT
PhysicsWOOT

Programming

Introduction to Programming with Python
Thursday, May 22 - Aug 7
Sunday, Jun 15 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Tuesday, Jun 17 - Sep 2
Monday, Jun 30 - Sep 22

Intermediate Programming with Python
Sunday, Jun 1 - Aug 24
Monday, Jun 30 - Sep 22

USACO Bronze Problem Series
Tuesday, May 13 - Jul 29
Sunday, Jun 22 - Sep 1

Physics

Introduction to Physics
Wednesday, May 21 - Aug 6
Sunday, Jun 15 - Sep 14
Monday, Jun 23 - Sep 15

Physics 1: Mechanics
Thursday, May 22 - Oct 30
Monday, Jun 23 - Dec 15

Relativity
Sat & Sun, Apr 26 - Apr 27 (4:00 - 7:00 pm ET/1:00 - 4:00pm PT)
Mon, Tue, Wed & Thurs, Jun 23 - Jun 26 (meets every day of the week!)
0 replies
jlacosta
Apr 2, 2025
0 replies
Inequality with a,b,c
GeoMorocco   7
N 10 minutes ago by math90
Source: Morocco Training 2025
Let $   a,b,c   $ be positive real numbers such that : $   ab+bc+ca=3   $ . Prove that : $$\frac{a\sqrt{3+bc}}{b+c}+\frac{b\sqrt{3+ca}}{c+a}+\frac{c\sqrt{3+ab}}{a+b}\ge a+b+c $$
7 replies
GeoMorocco
Thursday at 9:51 PM
math90
10 minutes ago
Combinatorics game
VicKmath7   3
N 20 minutes ago by Topiary
Source: First JBMO TST of France 2020, Problem 1
Players A and B play a game. They are given a box with $n=>1$ candies. A starts first. On a move, if in the box there are $k$ candies, the player chooses positive integer $l$ so that $l<=k$ and $(l, k) =1$, and eats $l$ candies from the box. The player who eats the last candy wins. Who has winning strategy, in terms of $n$.
3 replies
VicKmath7
Mar 4, 2020
Topiary
20 minutes ago
Find all such primes
Entrepreneur   2
N 25 minutes ago by straight
Source: Own
Find all primes $p,q\;\&\;r$ such that $$\color{blue}{pq=r^2+r+1.}$$
2 replies
Entrepreneur
an hour ago
straight
25 minutes ago
Inspired by giangtruong13
sqing   5
N 33 minutes ago by kokcio
Source: Own
Let $ a,b,c,d\geq 0 ,a-b+d=21 $ and $ a+3b+4c=101 $. Prove that
$$ 61\leq  a+b+2c+d\leq \frac{265}{3}$$$$- \frac{2121}{2}\leq   ab+bc-2cd+da\leq \frac{14045}{12}$$$$\frac{519506-7471\sqrt{7471}}{27}\leq   ab+bc-2cd+3da\leq 33620$$
5 replies
sqing
Yesterday at 2:57 AM
kokcio
33 minutes ago
Final epic for 2014
EpicSkills32   1
N Dec 2, 2016 by Kagebaka
$\ [\text{Blog Post 141}] $
Notes to self (to-do/stuff to blog about):
[list][*]Family camp (where I saw programming1157)
[*]Christmas vacation
[*]European dodgeball
[*]PSAT and SAT[/list]
well darn can't remember anything else. . .

But before I talk about that stuff, I'm gonna take the little time at the end of this year to talk about . . . this year.
Later I'll make some more in-depth observations and reflections, but for now I just need to get on here and share some long-overdue stuff, mostly music that I've found recently but still haven't shared.

$\dfrac{\text{Epic}}{\text{Item(s)}} 171-191 $

Electronic music!

Oh and I just have to say right now that Oliver Twist has, literally, the best plot of any story (film or book) ever. (Ok there are probably others that I've read/seen before, but I've read Oliver Twist twice now and both times after finishing it I've thought "dayum that was good.")

Well I guess that's it for tonight; it's almost 1:00 A.M. so yea. . . Goin bowling tomorrow with a bunch of guys from a sort-of church group.
I'll probably edit this post or make a new one with stuff I forgot, and, oh yeah, music from other genres XP
1 reply
EpicSkills32
Dec 30, 2014
Kagebaka
Dec 2, 2016
No more topics!
Easy problem from kyiv festival
rogue   6
N Mar 23, 2012 by TheStrayCat
Source: 5-th Kyiv math festival, 2006
See all the problems from 5-th Kyiv math festival here


Triangle $ABC$ and straight line $l$ are given at the plane. Construct using a compass and a ruler the straightline which is parallel to $l$ and bisects the area of triangle $ABC.$
6 replies
rogue
May 14, 2006
TheStrayCat
Mar 23, 2012
Easy problem from kyiv festival
G H J
Source: 5-th Kyiv math festival, 2006
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
rogue
553 posts
#1 • 2 Y
Y by Adventure10, Mango247
See all the problems from 5-th Kyiv math festival here


Triangle $ABC$ and straight line $l$ are given at the plane. Construct using a compass and a ruler the straightline which is parallel to $l$ and bisects the area of triangle $ABC.$
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
yetti
2643 posts
#2 • 2 Y
Y by Adventure10, Mango247
Lines dividing the triangle area in half are tangent to 3 hyperbolic segments, each having 2 triangle side lines as asyptotes, and each touching 2 medians at their midpoints, the 2 medians not passing through the intersection of asymptotes. First, draw 3 lines parallel to the given line through the triangle vertices. One of these lines goes through the triangle interior. Eliminate the hyperbola having the intersection of asymptotes at this vertex. The focal points of the remaining hyperbolas are particulary easy to construct, when the triangle $\triangle ABC$ is projected by a parallel projection into an isosceles right triangle $\triangle A'B'C'$ with the angle $\angle A' = 90^\circ.$ One focal point of the normal hyperbola with the asymptotes A'B', A'C' is the midpoint F of B'C', the other one a reflection F' of F in A'. One hyperbola vertex is on the ray A'F at $A'V = A'F \frac{\sqrt 2}{2}$, the other is a reflection V' of V in A'. Circle (A') centered at A' and with radius A'V = A'V' is the hyperbola pedal circle. A normal to the line $l'$ (obtained from $l$ by the used parallel projection) through the focus F meets the pedal circle (A') at points P, Q. Parallels to $l'$ through P, Q are hyperbola tangents. One is tangent to the other hyperbola branch and it does not cut the triangle at all. If the other one touches the hyperbola branch passing through the triangle $\triangle A'B'C'$ on the hyperbolic segment MN, where M, N are midpoints of B'- and C'- medians (i.e., the constructed parallel to $l'$ intersects the segments A'B', A'C'), it divides in half the triangle area.
Attachments:
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
TheStrayCat
161 posts
#3 • 2 Y
Y by Adventure10, Mango247
My solution is somewhat easier. :)
It isn't difficult to prove that for at least one of the vertices (for example, $ B$) the line passing through this vertice and parallel to $ l$ contains points within the triangle and divides it into two parts. Let $ T$ be the point of intersection of this line and $ AC$, we assume that $ AT > TC$ (if $ AT = TC$ everything is clear), also let $ l_1$ be the line we need to construct.
Denote by $ X$ and $ Y$ the points of intersection $ l_1$ with $ AB$ and $ AC$ respectively. Apparently, $ 2*AX*AY = AB*AC$ and $ \frac {AX}{AY} = \frac {AB}{AT}$. Multiplying these two equations, we obtain $ 2AX^2 = \frac {AB^2 *AC}{AT}$, whence we can easily construct the length of $ AX$ and the line $ l_1$ therefore.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
SCP
1502 posts
#4 • 2 Y
Y by Adventure10, Mango247
BlackMax wrote:
We obtain $ 2AX^2 = \frac {AB^2 *AC}{AT}$, whence we can easily construct the length of $ AX$ and the line $ l_1$ therefore.

I suppose we first make a way to construct the lengt of $AX$ at some way, but how would you place it parallel with $l_1$, can you write out your solution complete, so we can see if it is simpler?
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
TheStrayCat
161 posts
#5 • 2 Y
Y by Adventure10, Mango247
SCP wrote:
I suppose we first make a way to construct the lengt of $AX$ at some way, but how would you place it parallel with $l_1$, can you write out your solution complete, so we can see if it is simpler?

What exactly are you interested in, the way I construct $X$ or how to draw a parallel line? The latter is trivial when the line and one point is given. As to expressing $AX$, we know it equals $AX=\frac{1}{\sqrt{2}}AB\sqrt {\frac{AC}{AT}}$. Since we know how to construct a proportional segment if three others are given, and how to construct the geometrical mean, we rewrite the needed expression as $\frac{\sqrt{AB*AC}\sqrt{AB*AT}}{AT}$ and after a chain of transformations obtain a segment equivalent to $AX$.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
SCP
1502 posts
#6 • 2 Y
Y by Adventure10, Mango247
BlackMax wrote:
$AX=\frac{\sqrt{AB*AC}\sqrt{AB*AT}}{AT}$

Yes, all you wrote, I agree, but you always tell, you can construct the length easily:
so you can construct length $\sqrt{AB*AC}$ and similar at an easy way (I don't know, but seems it will have an easy way, but how?) and how do you finish a length $xy/z$ if $x,y,z$ are already constructed?
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
TheStrayCat
161 posts
#7 • 2 Y
Y by Adventure10, Mango247
SCP wrote:
BlackMax wrote:
$AX=\frac{\sqrt{AB*AC}\sqrt{AB*AT}}{AT}$

Yes, all you wrote, I agree, but you always tell, you can construct the length easily:
so you can construct length $\sqrt{AB*AC}$ and similar at an easy way (I don't know, but seems it will have an easy way, but how?) and how do you finish a length $xy/z$ if $x,y,z$ are already constructed?

For example, if we have two segments with lengths $a$ and $b$, we can take another segment $AC=a+b$, the point $B$ on it such that $AB=a$, $BC=b$. Then by using $AC$ as the diameter to draw a circle containing $A$ and $C$ and intersecting it with a straight line through $B$ perpendicular to $AC$, we'll get two segments $\sqrt{ab}$ units long.

The second one uses the intercept theorem and drawing a parallel line through a given point.

Would I be at the contest writing the solution, I'd mention how they are obtained, just to stay on the safe side, but here I suppose that any user with basic experience in solving construction problems outside a school textbook must be familiar with common auxilliary lemmas.
Z K Y
N Quick Reply
G
H
=
a