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Alex Ortiz's user avatar
Alex Ortiz's user avatar
Alex Ortiz's user avatar
Alex Ortiz
  • Member for 8 years, 5 months
  • Last seen this week
  • Cambridge, MA, USA
33 votes
Accepted

What's the Cartesian Product of $\{x\}$ and $\{x\}$?

30 votes

Can someone give me an example of a challenging proof by induction?

26 votes

convergence in $L^p$ implies convergence in measure

25 votes
Accepted

Intuition/meaning behind quadratic forms

20 votes

Showing $\frac{\sin x}{x}$ is NOT Lebesgue Integrable on $\mathbb{R}_{\ge 0}$

17 votes

How do you understand Infinitesimals?

16 votes
Accepted

Solve $ \int_0^2 \sqrt{x+\sqrt{x+\sqrt{x+\dotsb}}}\,dx $

16 votes
Accepted

Factorial equation: why does $n!\cdot(n + 2)! = n\cdot(n + 2)!\cdot(n - 1)!$

14 votes

difference between hyperplane and plane, examples, pictures

14 votes
Accepted

Fourier Transformation of $e^{-a|x|}$

14 votes
Accepted

"Let" in math texts

12 votes
Accepted

Dominated convergence theorem - what sequence?

12 votes

How to be good at coming up with counter example in Topology

12 votes
Accepted

Isomorphism $f$ preserves the order of an element?

12 votes

is a quotient of a free module free? Is a direct sum of free modules free?

12 votes
Accepted

For $f:X\rightarrow Y,$ if $f$ is continuous and $X$ is a complete metric space, does $f$ preserve Cauchy sequences?

11 votes

What is the term given to two functions when their order of composition does not matter?

11 votes
Accepted

Can a smooth map be extended to an open set?

10 votes

How can one prove that manifolds are regular?

10 votes
Accepted

What does "spans" and "spanned by" mean in the context of linear algebra?

9 votes

Examples of limits in nature with $\lim_{x \to c}f(x) \neq f(c)$

9 votes
Accepted

Explain to 10 year old: "Don’t talk about percentages of numbers when the numbers might be negative."

9 votes
Accepted

In what sense is an orientation continuous?

9 votes

Intuition for why any square matrix is a sum of a symmetric matrix and a skew-symmetric matrix?

8 votes
Accepted

Convolution of L^p and L^q function is uniformly continuous or not?

8 votes

Is there a bijective function mapping Natural numbers to Natural numbers, other than $f(n) = n$?

8 votes
Accepted

Is this valid way to prove $(-1)(-1) = 1$?

7 votes

Proving the Exterior (Outer) Measure of Rectangle is Equal to Volume

7 votes
Accepted

Is the maximal atlas for a topological manifold unique?

7 votes
Accepted

Proof Reference For Doob's First Stopping Time Theorem

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