Join our FREE webinar on May 1st to learn about managing anxiety.

G
Topic
First Poster
Last Poster
Tilted Students Thoroughly Splash Tiger part 2
DottedCaculator   18
N 44 minutes ago by MathLuis
Source: ELMO 2024/5
In triangle $ABC$ with $AB<AC$ and $AB+AC=2BC$, let $M$ be the midpoint of $\overline{BC}$. Choose point $P$ on the extension of $\overline{BA}$ past $A$ and point $Q$ on segment $\overline{AC}$ such that $M$ lies on $\overline{PQ}$. Let $X$ be on the opposite side of $\overline{AB}$ from $C$ such that $\overline{AX} \parallel \overline{BC}$ and $AX=AP=AQ$. Let $\overline{BX}$ intersect the circumcircle of $BMQ$ again at $Y \neq B$, and let $\overline{CX}$ intersect the circumcircle of $CMP$ again at $Z \neq C$. Prove that $A$, $Y$, and $Z$ are collinear.

Tiger Zhang
18 replies
DottedCaculator
Jun 21, 2024
MathLuis
44 minutes ago
Putnam 1958 February A5
sqrtX   4
N 5 hours ago by Safal
Source: Putnam 1958 February
Show that the integral equation
$$f(x,y) = 1 + \int_{0}^{x} \int_{0}^{y} f(u,v) \, du \, dv$$has at most one solution continuous for $0\leq x \leq 1, 0\leq y \leq 1.$
4 replies
sqrtX
Jul 18, 2022
Safal
5 hours ago
Miklós Schweitzer 1956- Problem 1
Coulbert   1
N Today at 1:30 PM by NODIRKHON_UZ
1. Solve without use of determinants the following system of linear equations:

$\sum_{j=0}{k} \binom{k+\alpha}{j} x_{k-j} =b_k$ ($k= 0,1, \dots , n$),

where $\alpha$ is a fixed real number. (A. 7)
1 reply
Coulbert
Oct 9, 2015
NODIRKHON_UZ
Today at 1:30 PM
D1021 : Does this series converge?
Dattier   3
N Today at 1:21 PM by Dattier
Source: les dattes à Dattier
Is this series $\sum \limits_{k\geq 1} \dfrac{\ln(1+\sin(k))} k$ converge?
3 replies
Dattier
Apr 26, 2025
Dattier
Today at 1:21 PM
If a matrix exponential is identity, does it follow the initial matrix is zero?
bakkune   5
N Today at 12:45 PM by loup blanc
This might be a really dumb question, but I have neither a rigorous proof nor a counter example.

For any square matrix $\mathbf{A}$, define
$$
e^{\mathbf{A}} = \mathbf{I} + \sum_{n=1}^{+\infty} \frac{1}{n!}\mathbf{A}^n
$$where $\mathbf{I}$ is the identity matrix. If for some matrix $\mathbf{A}$ that $e^{\mathbf{A}}$ is identity, does it follow that $\mathbf{A}$ is zero?
5 replies
bakkune
Mar 4, 2025
loup blanc
Today at 12:45 PM
Range of 2 parameters and Convergency of Improper Integral
Kunihiko_Chikaya   3
N Today at 11:37 AM by Mathzeus1024
Source: 2012 Kyoto University Master Course in Mathematics
Let $\alpha,\ \beta$ be real numbers. Find the ranges of $\alpha,\ \beta$ such that the improper integral $\int_1^{\infty} \frac{x^{\alpha}\ln x}{(1+x)^{\beta}}$ converges.
3 replies
Kunihiko_Chikaya
Aug 21, 2012
Mathzeus1024
Today at 11:37 AM
Matrix Row and column relation.
Schro   6
N Today at 6:20 AM by Schro
If ith row of a matrix A is dependent,Then ith column of A is also dependent and vice versa .

Am i correct...
6 replies
Schro
Apr 28, 2025
Schro
Today at 6:20 AM
A small problem in group theory
qingshushuxue   2
N Today at 4:42 AM by qingshushuxue
Assume that $G,A,B,C$ are group. If $G=\left( AB \right) \bigcup \left( CA \right)$, prove that $G=AB$ or $G=CA$.

where $$A,B,C\subset G,AB\triangleq \left\{ ab:a\in A,b\in B \right\}.$$
2 replies
qingshushuxue
Today at 2:06 AM
qingshushuxue
Today at 4:42 AM
Putnam 1958 February A4
sqrtX   2
N Today at 2:14 AM by centslordm
Source: Putnam 1958 February
If $a_1 ,a_2 ,\ldots, a_n$ are complex numbers such that
$$ |a_1| =|a_2 | =\cdots = |a_n| =r \ne 0,$$and if $T_s$ denotes the sum of all products of these $n$ numbers taken $s$ at a time, prove that
$$ \left| \frac{T_s }{T_{n-s}}\right| =r^{2s-n}$$whenever the denominator of the left-hand side is different from $0$.
2 replies
sqrtX
Jul 18, 2022
centslordm
Today at 2:14 AM
analysis
Hello_Kitty   2
N Yesterday at 10:37 PM by Hello_Kitty
what is the range of $f=x+2y+3z$ for any positive reals satifying $z+2y+3x<1$ ?
2 replies
Hello_Kitty
Yesterday at 9:59 PM
Hello_Kitty
Yesterday at 10:37 PM
Putnam 1958 February A1
sqrtX   2
N Yesterday at 10:32 PM by centslordm
Source: Putnam 1958 February
If $a_0 , a_1 ,\ldots, a_n$ are real number satisfying
$$ \frac{a_0 }{1} + \frac{a_1 }{2} + \ldots + \frac{a_n }{n+1}=0,$$show that the equation $a_n x^n + \ldots +a_1 x+a_0 =0$ has at least one real root.
2 replies
sqrtX
Jul 18, 2022
centslordm
Yesterday at 10:32 PM
n variables with n-gon sides
mihaig   0
Apr 25, 2025
Source: Own
Let $n\geq3$ and let $a_1,a_2,\ldots, a_n\geq0$ be reals such that $\sum_{i=1}^{n}{\frac{1}{2a_i+n-2}}=1.$
Prove
$$\frac{24}{(n-1)(n-2)}\cdot\sum_{1\leq i<j<k\leq n}{a_ia_ja_k}\geq3\sum_{i=1}^{n}{a_i}+n.$$
0 replies
mihaig
Apr 25, 2025
0 replies
n variables with n-gon sides
G H J
G H BBookmark kLocked kLocked NReply
Source: Own
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
mihaig
7352 posts
#1
Y by
Let $n\geq3$ and let $a_1,a_2,\ldots, a_n\geq0$ be reals such that $\sum_{i=1}^{n}{\frac{1}{2a_i+n-2}}=1.$
Prove
$$\frac{24}{(n-1)(n-2)}\cdot\sum_{1\leq i<j<k\leq n}{a_ia_ja_k}\geq3\sum_{i=1}^{n}{a_i}+n.$$
Z K Y
N Quick Reply
G
H
=
a