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Elias Costa

Member for 12 years, 10 months
Last seen this week

Brasília, DF, Brasil

Summary

Reputation

14,916

14.9k
13.5k
12.1k

2021
2022
2023
2024

Top tag

real-analysis

Next privilege

15,000 Rep.

Protect questions

Badges

5

54

89

Newest

Necromancer

Next badge

394/500

Copy Editor

Impact

~1.2m

people reached

142

helpful flags

2,217

votes cast

Answers

View all 461 answers

47

How can I prove that $xy\leq x^2+y^2$?

Apr 10, 2013

39

How does a non-mathematician go about publishing a proof in a way that ensures it to be up to the mathematical community's standards?

Jan 10, 2013

27

Why the $\nabla f(x)$ in the direction orthogonal to $f(x)$?

May 25, 2013

21

Can't argue with success? Looking for "bad math" that "gets away with it"

Dec 18, 2012

15

Funny identities

Jan 13, 2013

Questions

View all 118 questions

123

On the Constant Rank Theorem and the Frobenius Theorem for differential equations.

Jun 22, 2013

71

How to prove that a compact set in a Hausdorff topological space is closed?

Nov 18, 2011

31

A simple way to obtain $\prod_{p\in\mathbb{P}}\frac{1}{1-p^{-s}}=\sum_{n=1}^{\infty}\frac{1}{n^s}$.

Jun 24, 2013

25

Prove that $2018^{2019}> 2019^{2018}$ without induction, without Newton's binomial formula and without Calculus.

Feb 25, 2019

22

What distinguishes measure theory and probability theory?

Mar 9, 2012

Tags

View all 263 tags

real-analysis

205

Score

134

posts

calculus

135

Score

92

posts

integration

67

Score

40

posts

soft-question

67

Score

17

posts

linear-algebra

66

Score

50

posts

Reputation

+10

Check my proof that $(ab)^{-1} = b^{-1} a^{-1}$

+10

How to prove that a compact set in a Hausdorff topological space is closed?

+10

Examples of dictionaries between two distinct fields of mathematics (or between "differents" structures of math).

+10

On the Constant Rank Theorem and the Frobenius Theorem for differential equations.

Badges

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5

gold badges

Great Question

Nov 13, 2022
Electorate

Jul 22, 2013
Steward

Dec 6, 2014

54

silver badges

Sportsmanship

Sep 12, 2021
Deputy

Apr 24, 2014
Strunk & White

Jan 4, 2013

89

bronze badges

real-analysis

Mar 7, 2016
Tag Editor

Dec 8, 2012
calculus

Dec 27, 2017

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Votes cast

2,099

upvotes

118

downvotes

1,302

question votes

915

answer votes

1

this month