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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.

Introductory: Grades 5-10

Prealgebra 1 Self-Paced

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0 replies
jlacosta
Apr 2, 2025
0 replies
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Introducing myself at AoPS, and what's your magic wand?
asuth_asuth   1047
N 3 hours ago by RadioDemon666
Hi!

I'm Andrew Sutherland. I'm the new Chief Product Officer at AoPS. As you may have read, Richard is retiring and Ben Kornell and I are working together to lead the company now. I'm leading all the software and digital stuff at AoPS. I just wanted to say hello and introduce myself! I'm really excited to be part of the special community that is AoPS.

Previously, I founded Quizlet as a 15-year-old high school student. I did Course 6 at MIT and then left to lead Quizlet full-time for a total of 14 years. I took a few years off and now I'm doing AoPS! I wrote more about all that on my blog: https://asuth.com/im-joining-aops

I have a question for all of you. If you could wave a magic wand, and change anything about AoPS, what would it be? All suggestions welcome! Thank you.
1047 replies
asuth_asuth
Mar 30, 2025
RadioDemon666
3 hours ago
J
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Three variables inequality
Headhunter   6
N 4 hours ago by lbh_qys
$\forall a\in R$ ,$~\forall b\in R$ ,$~\forall c \in R$
Prove that at least one of $(a-b)^{2}$, $(b-c)^{2}$, $(c-a)^{2}$ is not greater than $\frac{a^{2}+b^{2}+c^{2}}{2}$.

I assume that all are greater than it, but can't go more.
6 replies
Headhunter
Apr 20, 2025
lbh_qys
4 hours ago
J
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Sequence
lgx57   8
N 5 hours ago by Vivaandax
$a_1=1,a_{n+1}=a_n+\frac{1}{a_n}$. Find the general term of $\{a_n\}$.
8 replies
lgx57
Apr 27, 2025
Vivaandax
5 hours ago
J
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Geometric inequality
ReticulatedPython   3
N 5 hours ago by ItalianZebra
Let $A$ and $B$ be points on a plane such that $AB=n$, where $n$ is a positive integer. Let $S$ be the set of all points $P$ such that $\frac{AP^2+BP^2}{(AP)(BP)}=c$, where $c$ is a real number. The path that $S$ traces is continuous, and the value of $c$ is minimized. Prove that $c$ is rational for all positive integers $n.$
3 replies
ReticulatedPython
Apr 22, 2025
ItalianZebra
5 hours ago
J
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This has been going on for a while now, can anyone else relate?
jmr2010   2
N Today 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
Yesterday at 7:16 PM
valisaxieamc
Today at 3:02 AM
J
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Cannot post PHP
char0221   2
N Today 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
Today at 1:23 AM
bpan2021
Today at 2:01 AM
J
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Transformation of a cross product when multiplied by matrix A
Math-lover1   1
N Today at 1:02 AM by greenturtle3141
I was working through AoPS Volume 2 and this statement from Chapter 11: Cross Products/Determinants confused me.
[quote=AoPS Volume 2]A quick comparison of $|\underline{A}|$ to the cross product $(\underline{A}\vec{i}) \times (\underline{A}\vec{j})$ reveals that a negative determinant [of $\underline{A}$] corresponds to a matrix which reverses the direction of the cross product of two vectors.[/quote]
I understand that this is true for the unit vectors $\vec{i} = (1 \ 0)$ and $\vec{j} = (0 \ 1)$, but am confused on how to prove this statement for general vectors $\vec{v}$ and $\vec{w}$ although its supposed to be a quick comparison.

How do I prove this statement easily with any two 2D vectors?
1 reply
Math-lover1
Yesterday at 10:29 PM
greenturtle3141
Today at 1:02 AM
J
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Geometry books
T.Mousavidin   4
N Today at 12:10 AM by compoly2010
Hello, I wanted to ask if anybody knows some good books for geometry that has these topics in:
Desargues's Theorem, Projective geometry, 3D geometry,
4 replies
T.Mousavidin
Yesterday at 4:25 PM
compoly2010
Today at 12:10 AM
J
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trigonometric functions
VivaanKam   3
N Yesterday at 10:08 PM by aok
Hi could someone explain the basic trigonometric functions to me like sin, cos, tan etc.
Thank you!
3 replies
VivaanKam
Yesterday at 8:29 PM
aok
Yesterday at 10:08 PM
J
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k How to remove tags from a PM after you've removed yourself from it
Platinum_Dragon   2
N Yesterday 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
Yesterday at 7:25 PM
Platinum_Dragon
Yesterday at 7:32 PM
J
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Inequalities
sqing   16
N Yesterday at 5:25 PM by martianrunner
Let $ a,b \in [0 ,1] . $ Prove that
$$\frac{a}{ 1-ab+b }+\frac{b }{ 1-ab+a } \leq 2$$$$ \frac{a}{ 1+ab+b^2 }+\frac{b }{ 1+ab+a^2 }+\frac{ab }{2+ab } \leq 1$$$$\frac{a}{ 1-ab+b^2 }+\frac{b }{ 1-ab+a^2 }+\frac{1 }{1+ab }\leq \frac{5}{2}$$$$\frac{a}{ 1-ab+b^2 }+\frac{b }{ 1-ab+a^2 }+\frac{1 }{1+2ab }\leq \frac{7}{3}$$$$\frac{a}{ 1+ab+b^2 }+\frac{b }{ 1+ab+a^2 } +\frac{ab }{1+ab }\leq \frac{7}{6 }$$
16 replies
sqing
Apr 25, 2025
martianrunner
Yesterday at 5:25 PM
J
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Geometry Angle Chasing
Sid-darth-vater   6
N Yesterday at 2:18 PM by sunken rock
Is there a way to do this without drawing obscure auxiliary lines? (the auxiliary lines might not be obscure I might just be calling them obscure)

For example I tried rotating triangle MBC 80 degrees around point C (so the BC line segment would now lie on segment AC) but I couldn't get any results. Any help would be appreciated!
6 replies
Sid-darth-vater
Apr 21, 2025
sunken rock
Yesterday at 2:18 PM
J
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BABBAGE'S THEOREM EXTENSION
Mathgloggers   0
Yesterday at 12:18 PM
A few days ago I came across. this interesting result is someone interested in proving this.

$\boxed{\sum_{k=1}^{p-1} \frac{1}{k} \equiv \sum_{k=p+1}^{2p-1} \frac{1}{k} \equiv \sum_{k=2p+1}^{3p-1}\frac{1}{k} \equiv.....\sum_{k=p(p-1)+1}^{p^2-1}\frac{1}{k} \equiv 0(mod p^2)}$
0 replies
Mathgloggers
Yesterday at 12:18 PM
0 replies
J
H
N.S. condition of passing a fixed point for a function
Kunihiko_Chikaya   1
N Yesterday at 11:29 AM by Mathzeus1024
Let $ f(t)$ be a function defined in any real numbers $ t$ with $ f(0)\neq 0.$ Prove that on the $ x-y$ plane, the line $ l_t : tx+f(t) y=1$ passes through the fixed point which isn't on the $ y$ axis in regardless of the value of $ t$ if only if $ f(t)$ is a linear function in $ t$.
1 reply
Kunihiko_Chikaya
Sep 6, 2009
Mathzeus1024
Yesterday at 11:29 AM
J
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J
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k How to delete my post easily?
whwlqkd   17
N Apr 7, 2025 by whwlqkd
How to delete my post(trash) easily and fast?
17 replies
whwlqkd
Apr 6, 2025
whwlqkd
Apr 7, 2025
J
How to delete my post easily?
G H J
Reveal topic tags
L
G H BBookmark kLocked kLocked NReply
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whwlqkd
97 posts
whwlqkd
#1 h  Apr 6, 2025, 3:04 PM • 1 Y
Y by PikaPika999
How to delete my post(trash) easily and fast?
Z Y
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EaZ_Shadow
1234 posts
EaZ_Shadow
#2 h  Apr 6, 2025, 3:08 PM • 1 Y
Y by PikaPika999
U cant. Once someone post after you, you can only edit
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SomeonecoolLovesMaths
3209 posts
SomeonecoolLovesMaths
#3 h  Apr 6, 2025, 3:26 PM • 1 Y
Y by PikaPika999
Ask the mods ig
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TeddySava
60 posts
TeddySava
#4 h  Apr 6, 2025, 3:32 PM • 1 Y
Y by PikaPika999
Can you edit somebody else's post?
Z Y
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SomeonecoolLovesMaths
3209 posts
SomeonecoolLovesMaths
#5 h  Apr 6, 2025, 3:34 PM • 1 Y
Y by PikaPika999
TeddySava wrote:
Can you edit somebody else's post?

A mod can
Z Y
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Skandaharini
53 posts
Skandaharini
#6 h  Apr 6, 2025, 3:34 PM • 1 Y
Y by PikaPika999
How do you edit your post
Z Y
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Skandaharini
53 posts
Skandaharini
#7 h  Apr 6, 2025, 3:35 PM • 1 Y
Y by PikaPika999
Can you delete your post if no one posts anything after you
Z Y
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Craftybutterfly
410 posts
Craftybutterfly
#8 h  Apr 6, 2025, 4:08 PM • 1 Y
Y by PikaPika999
Ask mod or admin to do it unless your one
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MathWinner121
444 posts
MathWinner121
#9 h  Apr 6, 2025, 4:14 PM • 1 Y
Y by PikaPika999
you can edit, delete the words, and type redacted
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SomeonecoolLovesMaths
3209 posts
SomeonecoolLovesMaths
#10 h  Apr 6, 2025, 4:14 PM • 1 Y
Y by PikaPika999
Skandaharini wrote:
How do you edit your post

By clicking the pencil like button in place of the like button.
Z Y
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SomeonecoolLovesMaths
3209 posts
SomeonecoolLovesMaths
#11 h  Apr 6, 2025, 4:15 PM • 1 Y
Y by PikaPika999
Skandaharini wrote:
Can you delete your post if no one posts anything after you

Yes, for a certain period of time. I guess you cannot anymore after a certain amount of time has passed, I forgot how much tho.
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Craftybutterfly
410 posts
Craftybutterfly
#12 h  Apr 6, 2025, 4:19 PM • 1 Y
Y by PikaPika999
SomeonecoolLovesMaths wrote:
Skandaharini wrote:
Can you delete your post if no one posts anything after you

Yes, for a certain period of time. I guess you cannot anymore after a certain amount of time has passed, I forgot how much tho.

Until someone posts after you
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AlienGirl05
11696 posts
AlienGirl05
#13 h  Apr 6, 2025, 4:20 PM • 2 Y
Y by PikaPika999, whwlqkd
whwlqkd wrote:
How to delete my post(trash) easily and fast?

Report your post, and ask AoPSSheriff to delete it. :)
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K124659
2575 posts
K124659
#14 h  Apr 6, 2025, 7:19 PM • 3 Y
Y by PikaPika999, AlienGirl05, whwlqkd
An alternate way is that if you want to delete a post for the purpose of solely redacting its contents, you can just edit the post, delete what you originally said, and input a text like "redacted" or "$~~~~~~~~~~~~~$"
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AlienGirl05
11696 posts
AlienGirl05
#15 h  Apr 6, 2025, 8:33 PM • 1 Y
Y by CoolBroCubby
K124659 wrote:
An alternate way is that if you want to delete a post for the purpose of solely redacting its contents, you can just edit the post, delete what you originally said, and input a text like "redacted" or "$~~~~~~~~~~~~~$"

Note: That only works when the thread in question is not locked. :)
This post has been edited 1 time. Last edited by AlienGirl05, Apr 6, 2025, 8:33 PM
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HacheB2031
391 posts
HacheB2031
#17 h  Apr 6, 2025, 11:28 PM
Y by
HacheB2031 wrote:
Post Here! (sorry for bump) (#16)

This post doesn't exist anymore. @bove is #15 and this is #17. Is this what you mean by deleting posts? EDIT: oh wait posts that have a post after them can't be deleted
This post has been edited 3 times. Last edited by HacheB2031, Apr 6, 2025, 11:32 PM
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Skandaharini
53 posts
Skandaharini
#19 h  Apr 7, 2025, 12:54 AM
Y by
ok thank you for answering my questions :)
This post has been edited 1 time. Last edited by Skandaharini, Apr 7, 2025, 12:54 AM
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whwlqkd
97 posts
whwlqkd
#20 h  Apr 7, 2025, 8:12 AM
Y by
AlienGirl05 wrote:
whwlqkd wrote:
How to delete my post(trash) easily and fast?

Report your post, and ask AoPSSheriff to delete it. :)

What a elegant way!!!
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