0
votes
0answers
5 views

Tangent space of quotient space

Let $\pi : M \rightarrow M/G$ be the canonical projection, where $M$ is a manifold and $M/G$ is a quotient manifold. Now, what can we say about $d \pi (p) : T_pM \rightarrow T_p(M/G)$? From my ...
0
votes
0answers
3 views

How to solve problems on alligation and mixture when three types are given?

Suppose there are three qualities of rice, A(1 dollar per Kg), b(2 dollar per Kg) and C(3 dollar per Kg). The salesmen want to mix these in a certain ratio a:b:c so as to make the price 2.5 dollar per ...
1
vote
0answers
13 views

How to prove every term of this sequence is not a natural number

Sorry for the repost and for my "bad" English. I made a lot of errors in the previous one, so here's my actual question: Let's take a look at this sequence: (1) $[a_1,a_2,a_3,a_4,...,a_x]$ where ...
-1
votes
0answers
5 views

new plane equation after transformation of coordinates

I have a plane equation $ax + by + cz + d = 0$ w.r.t to a particular coordinate frame. this coordinate frame w.r.t to the world coordinate frame is $$\begin{vmatrix} r_1 & r_2 & r_3 & ...
0
votes
0answers
16 views

Sine/cosine series

$$\frac{\sin²(1°) + \sin²(2°) + \sin²(3°) + .. + \sin²(90°)}{\cos²(1°) + \cos²(2°) + \cos²(3°) + .. + \cos²(90°)} = ?$$ I tried to use multiple identities but I couldn't simplify the expression. ...
2
votes
0answers
5 views

Why is every subgroup of a finitely generated nilpotent group closed in the profinite topology?

This should be a well known claim, but what is the proof? Why is every subgroup of a finitely generated nilpotent group closed in the profinite topology?
0
votes
0answers
9 views

Is $C[0,1]$ equipped with $\lVert \cdot \rVert_1$ a countable union of nowhere dense sets?

Let's consider the space of all continuous function $C[0,1]$ on the intervall $[0,1]$. But instead of using the usual supremum norm we use the $L^1$-Norm $: \lVert f \rVert_1=\int_0^1 \lvert f(x) ...
-2
votes
0answers
6 views

Behaviour of Fourier Inverse Transform after non-linear modulation

Suppose $\phi$ is a continuous nowhere differentiable function. $g$ some function in Schwartz space such that $\hat{g}$ has compact support. Define $f(x) = \int_{-\infty}^\infty ...
0
votes
1answer
15 views

Evaluate $\int_{-2}^{2}\int_{y^2-3}^{5-y^2}dxdy$

In the black I evaluated the integral and I got 64/3, now I need to evaluate the same integral with $\color{red}{dydx}$ .in the $\color{blue}{\text{blue}}$ color is my attempt, I don't think that my ...
5
votes
0answers
16 views

Asymptotic Behavior of a Sum with Binomial Coefficients

The Problem: Find the asymptotic behavior (with respect to $n$) of the following sum $$\sum\limits_{j = 3}^n \binom{n}{j} \frac{(j - 1)!}{2\cdot n^j}. $$ Where the Problem Comes From: If we ...
3
votes
0answers
10 views

Basic application of Weyl-Character-Formula

(I did not find a solution of my problem in any forum so far. Sorry if it exists...) I am new to Lie-Algebras and representations and actually do not need the mathematical background... I need only ...
0
votes
0answers
7 views

Need my CRT work spot-checked

So I have a bunch of equations that look like this: $$k + tx \equiv a \bmod m$$ Where $t$ is the common variable I am solving for among the equations (each equation may have different values for ...
1
vote
0answers
9 views

Differential geometry in the context of manifolds

I am an undergraduate student of mathematics. I have a solid background on calculus, linear algebra, real analysis and point set topology, but I have never studied differential geometry. I am very ...
4
votes
2answers
60 views

What is the domain of $f(x)=\frac{1}{x}-\frac{1}{x}$?

Question: What is the domain of $f(x)=\frac{1}{x}-\frac{1}{x}$? Does the function have a removable discontinuity at $x=0$? My attempt: My first intuition told me that it was $\mathbb R$, since we ...
0
votes
0answers
12 views

equally spaced on circle question

Define $$\|\vec{x}\|:=\sqrt{\alpha^2+\beta^2},$$ where $\vec{x}:=(\alpha,\beta)\in \mathbb{R}^2.$ Set $$\mathbb{S}^1:=\{\vec{x}\in \mathbb{R}^2: \|\vec{x}\|=1\}\quad \quad and\quad \quad ...
1
vote
1answer
8 views

What is the “Cumulative Distribution of the magnitude of the N-dimensional standard gaussian”

I am confused by this line from a paper: "Let $F_1(x)$ be the cumulative distribution of the magnitude of an $n$−dimensional standard Gaussian random variable and $F_2(x)$ be the cumulative ...
1
vote
0answers
8 views

Hypercenter is the intersection of normalizers of Sylow subgroups.

I'm trying to prove that the intersection of the normalizers of the Sylow subgroups of a [finite] group $G$ is equal to its hypercenter, i.e., $$Z_\infty(G)=\bigcap\limits_{S\in ...
0
votes
1answer
26 views

Trouble Solving a system of 3 equations

I'm having trouble solving a system of 3 equations. The set of equations in question is shown below $C_a=\frac{R_a}{\frac{R_a}{r_a}+\frac{R_b}{r_b}+\frac{R_c}{r_c}}, \quad ...
1
vote
1answer
21 views

Proper way to solve function notations?

I'm just starting to use function notation and I'm wondering if I'm solving correctly. If $f(x) = 4x - 11$, determine a. $f (1/4)$ $f(x) = 4x - 11$ $f(1/4) = 4 (1/4) - 11$ $f(1/4) = 1 - 11 $ ...
0
votes
0answers
7 views

Choose $\rho$ such that $\rho$-norm minimizes the matrix condition number

I'm solving questions from am exam that I failed miserably, so I would love it if someone can take a look at my proof and make sure I'm not making any gross mistakes. In my proposed answer I didn't ...
-1
votes
0answers
38 views

A proposed method for further abstracting prime numbers [on hold]

I previously posted this but I framed it as a question and only inserted my results as an edit several days after the original post was created. Ulam's Spiral is a wonderful discovery. Obviously it ...
0
votes
1answer
15 views

How to solve $ \frac{1}{1+x}-\frac{c}{x}-2\log \left( \frac{1+x}{x}\right)+A=0$

How to find a solution to the following equation \begin{align*} \frac{1}{1+x}-\frac{c}{x}-2\log \left( \frac{1+x}{x}\right)+A=0 \end{align*} where $c$ and $A$ are some constants such that $c\ge 1$ ...
-4
votes
0answers
15 views

integrate very long expression using orthogonality in maple

I have very long expression and i must integrate it. i try to apply "orthogonality" on my equations to eliminate "X" and "Y" variables. Image Shows examples of Orthogonal Functions After execute the ...
0
votes
0answers
14 views

Taking derivate wrt a vector

I'm trying to read through Wiki's description of the Levenberg-Marquardt algorithm. I've taken linear algebra, but I've always been fuzzy about taking derivatives with respect to a vector and just ...
0
votes
0answers
10 views

Notation for polynomials and equating coefficients

I am reading a paper where they define $P_k(s_1,s_2|t)$ as a polynomial of degree $k$ in $s_1$ and $s_2$ given $t$. What does it mean "given $t$"? (I was thinking that each term looks like ...
2
votes
2answers
19 views

Proof that any finite subset of a lattice has a supremum.

Let $C\subseteq D$ where $C = \{c_{1}, c_{2},\ldots, c_{n}\}$ and $D$ is a lattice. I believe that this supremum is $((c_1 \vee c_2)\vee c_3)\vee \ldots \vee c_n)$ (sorry about the notation). However ...
0
votes
3answers
21 views

Exponential Growth and Decay Question: A Bacteria Culture Grows with Constant Relative Growth Rate.

A Bacteria Culture Grows with Constant Relative Growth Rate. The bacteria count was 400 after 2 hours and 25,600 after 6 hours. a) What is the relative growth rate? Express your answer as a ...
4
votes
3answers
61 views

Rule for squaring arbitrary powers?

This is a really simple question, but I don't know how to phrase it well enough for Google. I'm going through a proof and don't understand how: $$ (q^{2^{n+1}})^2 = q^{2^{n+2}} $$ I thought it would ...
1
vote
2answers
32 views

Right answer, wrong explanation, probability of grids?

Two unit squares are selected at random without replacement from an $n\times n$ grid of unit squares. Find the least positive integer $n$ such that the probability that the two selected squares are ...
1
vote
0answers
17 views

Which directed graphs correspond to “algebraic” diagrams?

Any diagram for which the question of commutativity make sence is a directed graph, but not any directed graph make the question meaningful. $\require{AMScd}$ \begin{CD} A @>>> B @. A ...
5
votes
3answers
77 views

Finding all real numbers x such that $x \lceil x \lceil x \lceil x \rceil \rceil \rceil = 88$

Question: Find all real numbers x such that $x \lceil x \lceil x \lceil x \rceil \rceil \rceil = 88$. The notation $\lceil x \rceil$ means: The least integer which is not less than $x$. My ...
0
votes
1answer
19 views

A question on use of square integrable functions

I'm approaching this from a physicist's perspective, so apologies for any inaccuracies (and lack of rigour). As far as I understand it, a square-integrable function $f(x)$ satisfies the condition ...
4
votes
1answer
37 views

Differentiability at a point $x$ with $f$ differentiable in $\mathbb R\backslash\{x\}$

I have a real function that satisfies: $f:\mathbb R\rightarrow\mathbb R$ is differentiable at $x$ for $x\neq x_0$. There is a full-measure set $T$ such that for any sequence $t_n\in T$ with ...
0
votes
4answers
33 views

How to find perpendicular vectors in 3D

Find all values of a such that the vector $q = \langle 2, a, –2\rangle$ is perpendicular to the vector $p = \langle –3, a, 5 \rangle$.
-1
votes
0answers
11 views

Is the constant group scheme for $\mathbb{Z}$ affine?

Is the constant group scheme for $\mathbb{Z}$ affine? It is said no in Gille's notes "INTRODUCTION TO REDUCTIVE GROUP SCHEMES OVER RINGS" 3.1, but I don't see why!
7
votes
2answers
57 views

Is the following a characterization of $\Bbb Q\cap\cal C$, where $\cal C$ is the Cantor set?

Let $A$ be an ordered set, with the following properties: $A$ is countable $A$ has a least and greatest element Between any two points with successors are points without successors; between any two ...
2
votes
0answers
17 views

The set $T=\{l\in\mathbb{N}: ml=nl \ \text{implies} \ m=n \}$ is inductive.

I'm trying to prove the following statement: $ml=nl$ implies $m=n$ for every $m,n,l\in \mathbb{N}$. So I defined the set $T=\{l\in\mathbb{N}: ml=nl \ \text{implies} \ m=n \}$ and if I prove that ...
4
votes
3answers
45 views

Find the maximum value of the fraction

Let $a$ and $b$ be positive integers satisfying $\frac{ab+1}{a+b}<\frac{3}{2}$. The maximum possible value of $\frac{a^3b^3+1}{a^3+b^3}$ is $\frac{p}{q}$, where $p$ and $q$ are relatively prime ...
0
votes
1answer
18 views

Linear algebra: proving transformation matrix between orthogonal basis is unitary

The vector space $V$ is equipped with a Hermitian scalar product and an orthonormal basis $\{e_1,\ldots,e_n\}$. A second orthonormal basis $\{e_1',\ldots,e_n'\}$ is related to the first one by ...
1
vote
1answer
12 views

Property of an almost additive sequence of functions

We say that a sequene of functions $\Phi=(\phi_n)_n$ is almost additive if there exists a constant $C > 0$ such that for every $n,m \in \mathbb{N}$ and $x\in \Lambda$ we have \begin{equation*} -C + ...
0
votes
0answers
11 views

How to multiply the elements within a vector using matrix operations (e.g., dot product)?

Suppose a vector $\vec{v}^T=(v_1, v_2, \ldots, v_n)^T$. To sum the elements within the vector, I can use the dot product with a column vector of ones, $\sum_i v_i = \vec{v}^T \cdot \vec{1}$. My ...
2
votes
1answer
10 views

Properties of unimodal functions

A probability density function $f$ is said to be unimodal if the value at which the maximum value of the function is attained is unique. I am reading some papers on econometrics that appear to use ...
1
vote
0answers
16 views

how to understand a matrix with order $O(n^{-1})$

I am reading a paper in which an assumption is that a matrix (for example $A_{n\times n}$) is $O(n^{-1})$. I have difficulty to understand that assumption. Does that mean the norm of the matrix is ...
-4
votes
0answers
22 views

limits of computation [on hold]

Design a Turing machine to accept strings over $\{0, 1\}$ that are palindromes, that is, $w = wR$. (Hint: Modify the machine that accepts $wwR$ (even-length palindromes) so that it also ...
0
votes
0answers
45 views

Any hint on : Every $A_{n}$ elemnt is $n$-cycles product. [on hold]

[Added explanation] I found this exercise as follows in Hungerford : Abstract algebra (3rd edition) page 236, exercise number 40. Stated as follows : C.40. Prove that every element of $A_{n}$ is ...
0
votes
1answer
23 views

C*-Algebra: Cyclic Elements

Given a locally compact Hausdorff space $\Omega$. Consider the C*-algebra: ...
1
vote
2answers
32 views

Generators in group $Z^*_{p}$

show that $g=2$ is a generator of group $Z^*_{19}$ Can anyone explain me how i can show in this example and generally that an element is a generator in a group?
1
vote
1answer
17 views

Show that there exists a non-negative integer $r$ s.t. $ker(T^r) = ker(T^{r+1})$.

Question: Let $V$ be an $n$-dimensional complex vector space, let $T: V \to V$ be a linear transformation. Show that there exists a non-negative integer $r$ s.t. $ker(T^r) = ker(T^{r+1})$. My ...
-5
votes
1answer
79 views

Does square difference prove that 1 = 2?

I was mathematically shown 1 = 2 by a function that states the following $$x^2-x^2 = x^2-x^2 $$ $$x(x-x)=(x-x)(x+x)$$ dividing by $(x-x)$ we get... $$x=x+x$$ $$ x=2x$$ $$1=2$$ I can see ...
1
vote
2answers
23 views

Modular Quadratic Equation

I'm trying to solve that equation: $x^2-3x-5\equiv0\pmod{343}$ I've completed the square as follows: $x^2-3x-5 \equiv x^2+340x-5\equiv(x+170)^2-170^2-5\pmod{343}\\ (x+170)^2 \equiv 93\pmod{343}\\ ...

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