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Questions tagged [integral-inequality]

By Michael Henderson
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For questions inequalities which involves integrals, like Cauchy-Bunyakovsky-Schwarz or Hölder's inequality. To be used with (inequality) tag.

1,018 questions
1 vote 0 answers 11 views

A simple special case of Gronwall's inequality for Dini derivatives

Let $I=[t_0,t_1)\subset \Bbb R$ an interval and $a,b,c\ge0$ with $a>c$. Assume that $f\colon I\to\Bbb R$ is a continuous function with $$\tag{1} f(t)-f(s)\le \int_s^t\left( -af(r)+be^{-cr} \right) ... user avatar Mars Plastic
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3 votes 3 answers 84 views

Functional inequality with integral function [closed]

Given a function $f:[0;1]\to[0;1]$ such that $f(x)\leq2\int_0^x f(t)dt$, prove that $f(x)=0$ $ \forall x\in [0;1]$. I've observed that the function has to be concave down in his domain and that $... user avatar Federico A
  • 33
1 vote 2 answers 71 views

Show that $\int_2^{+ \infty} \frac{\log(t)^2}{t(t-1)}dt \leq 4$

I couldn't prove this inequality $$ \int_2^{+ \infty} \frac{\log(t)^2}{t(t-1)}dt \leq 4 $$ I've tried integration by parts but it doesn't work. user avatar user47204
  • 55
2 votes 0 answers 38 views

What is the correct version of the Gronwall lemma? Can the sign of u(t) be variable?

In the various forms of the Grönwall lemma in integral form are stated for NON NEGATIVE function $\phi$ And this coincides with what is written my ... user avatar J.C.VegaO
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1 vote 0 answers 12 views

Integration over the intersection of a hypersphere and half spaces

For $x\in\mathbb{R}^n$, $u\in\mathbb{R}^n$ and $0<c<\Vert u\Vert$, how could I compute (or find the upper bound of) the following integral $$\int_{x^\top x =1,~\vert u^\top x\vert\leq c}1dx.$$ ... user avatar lazyleo
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1 vote 0 answers 23 views

Derivation of Hölder Inequality through Young's Inequaliy

I am having trouble following a proof where Young's Inequality is being used to derive Hölder's Inequality. More precisely, there is a particular and final step that utilizes integration in order to ... user avatar ThriceTheDaddySimon
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1 vote 1 answer 50 views

How to evaluate the following integral might be related to the modified Bessel Function of first kind?

Recently, I have encountered the following integral solution problem in my research. Because it involves special functions, I cannot successfully solve it in calculation. $$\mathbb{E}_{Z_{1},Z_{2},\... user avatar LZ981ko
  • 21
1 vote 0 answers 32 views

How to solve the following double integral with the Bessel function?

Recently, I have encountered the following integral solution problem in my research. Because it involves special functions, I cannot successfully solve it in calculation. $$\mathbb{E}_{Z_{1},Z_{2}} \... user avatar LZ981ko
  • 21
2 votes 0 answers 45 views

A Reverse Cauchy-Schwarz Inequality.

My question is closely related to the question here, where it was established that if $f:[a,b] \longrightarrow \mathbb{R}$ such that $f \in L^2([a,b])$ and there exists $M=M_f,m=m_f>0$ so that $m_f ... user avatar Guilherme
  • 1,427
1 vote 1 answer 66 views

Find number of continuous functions satisfying the equation $4\int_{0}^{\frac{3}{2}}f(x)dx+125\int_{0}^{\frac{3}{2}}\frac{dx}{\sqrt{f(x)+x^2}}=108$

The number of continuous functions $f:\left[0,\frac{3}{2}\right]\rightarrow (0,\infty)$ satisfying the equation$$4\int_{0}^{\frac{3}{2}}f(x)dx+125\int_{0}^{\frac{3}{2}}\frac{dx}{\sqrt{f(x)+x^2}}=108$$ ... user avatar Maverick
  • 7,092
1 vote 0 answers 16 views

Showing inequality for the norm of an integral equation

Let $\xi \in \mathbb{R}^2$, $\Phi \in C^0([0, +\infty[, \mathbb{R}^{2x2})$ a bounded function. Let $y:[0, +\infty[ \rightarrow \mathbb{R}^2$ a solution of the following integral equation, $$ y(x) = e^{... user avatar Mathieu
  • 577
2 votes 1 answer 36 views

Is this kind of inverse substitution justified?

I'm trying to prove that for every integer $n\geq 0$ we have $$\int_0^{\pi/2} (1+\cos t)^ndt\geq \frac{2^{n+1}-1}{n+1}.$$ I started out by rewriting the RHS as $\int_0^{1}(1+x)^ndx$ and substituting $... user avatar Aatu Turpeinen
  • 41
1 vote 2 answers 25 views

Inequality involving moments of a distribution [closed]

Let X be a real random variable. Under what conditions on the distribution do we have that $$\mathbb{E}( X^{2n + 2}) \geq \mathbb{E}( X^{2n}) \mathbb{E}( X^{2})$$ for all integer $n$? I tried using ... user avatar Kelly
  • 19
6 votes 1 answer 81 views

What functions satisfy $\int_a^b f(x) c(x) \, dx \ge 0$ for all convex functions $f$?

This is an attempt to generalize Prove that $\int_{0}^{2\pi}f(x)\cos(kx)dx \geq 0$ for every $k \geq 1$ given that $f$ is convex. Inspired by that question and the given answers, I have the ... user avatar Martin R
  • 87.3k
0 votes 0 answers 45 views

an integral inequality from "Inequality" by Hardy,Littlewood and Polya Chapter7

If $f\in C^1[0,1)$ and $f(0)=0$ , show that $\int_0^1\frac{|f(x)|^2}{x^2}dx\leq4\int_0^1|f^{'}(x)|^2dx$ The book solves the problem using variational method. But I want to seek for an elementary ... user avatar etoile
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