User Nick Peterson

102 votes

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What does "isomorphic" mean in linear algebra?

answered Jul 12, 2013 at 3:25

92 votes

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Integration with respect to counting measure.

answered Apr 22, 2014 at 4:36

65 votes

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Drunk man with a set of keys.

answered Dec 4, 2016 at 21:50

58 votes

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Fourier Transform of Derivative

answered Jun 27, 2013 at 14:47

56 votes

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Integral Inequality Absolute Value: $\left| \int_{a}^{b} f(x) g(x) \ dx \right| \leq \int_{a}^{b} |f(x)|\cdot |g(x)| \ dx$

answered Jun 25, 2013 at 16:33

50 votes

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Probability that a quadratic equation has real roots

answered Sep 8, 2020 at 19:23

44 votes

Why does L'Hopital's rule fail in calculating $\lim_{x \to \infty} \frac{x}{x+\sin(x)}$?

answered Mar 23, 2016 at 21:12

41 votes

What does expected value of sum of two discrete random variables mean?

answered Jun 27, 2013 at 12:08

31 votes

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What is the standard notation to represent the set of primes?

answered Jul 31, 2013 at 13:15

21 votes

For $f$ continuous, show $\lim_{n\to\infty} n\int_0^1 f(x)x^n\,dx = f(1).$

answered Jul 29, 2013 at 22:30

21 votes

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Prove that in a tree with maximum degree $k$, there are at least $k$ leaves

answered Jun 23, 2013 at 17:20

19 votes

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Showing that $U(2^n)$ is not cyclic for $n \ge 3$

answered Jul 14, 2013 at 17:19

19 votes

Two Circles Can Have At Most One Common Chord? (IMO)

answered Oct 19, 2016 at 3:45

16 votes

Injection $\mathbb N \times \mathbb N \times \mathbb N \to \mathbb N$

answered Dec 13, 2013 at 14:21

15 votes

Grandi's series contradiction

answered Jun 23, 2013 at 16:07

15 votes

But what is a continuous function?

answered Jan 29, 2019 at 20:19

15 votes

Infinite Cartesian product of countable sets is uncountable

answered Sep 22, 2013 at 2:03

15 votes

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Expected value of rolling dice until getting a $3$

answered Mar 3, 2014 at 22:20

13 votes

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Puzzled by $\lim\limits_{x \to - \infty} \sqrt{x^2+x}-x$

answered Jan 4, 2014 at 22:13

13 votes

pigeonhole principle clarification

answered Nov 17, 2016 at 4:31

13 votes

What is the intuition behind the formula for the average?

answered Dec 22, 2016 at 4:40

12 votes

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Prove that $2^n3^{2n}-1$ is always divisible by 17

answered Sep 8, 2013 at 23:10

12 votes

How to prove $\sum_{n=0}^{\infty} \frac{n^2}{2^n} = 6$?

answered Dec 5, 2013 at 13:45

12 votes

Integral of a function's derivative does not equal the original function?

answered Dec 21, 2016 at 4:52

11 votes

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Maclaurin Series for $\ln(x+\sqrt{1+x^2})$

answered Jun 22, 2013 at 20:52

11 votes

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Motivation for Jordan Canonical Form

answered Jun 22, 2013 at 5:30

11 votes

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"such that" logical symbol

answered Jun 29, 2013 at 13:48

11 votes

What is the derivative of $x\sin x$?

answered Jul 14, 2013 at 17:49

11 votes

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Notation used for integrals w.r.t. probability measures

answered Jan 6, 2014 at 16:38

11 votes

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Logarithm of Gaussian function is whether convex or nonconvex?

answered Jun 1, 2015 at 3:45

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818 Answers

What does "isomorphic" mean in linear algebra?

Integration with respect to counting measure.

Drunk man with a set of keys.

Fourier Transform of Derivative

Integral Inequality Absolute Value: $\left| \int_{a}^{b} f(x) g(x) \ dx \right| \leq \int_{a}^{b} |f(x)|\cdot |g(x)| \ dx$

Probability that a quadratic equation has real roots

Why does L'Hopital's rule fail in calculating $\lim_{x \to \infty} \frac{x}{x+\sin(x)}$?

What does expected value of sum of two discrete random variables mean?

What is the standard notation to represent the set of primes?

For $f$ continuous, show $\lim_{n\to\infty} n\int_0^1 f(x)x^n\,dx = f(1).$

Prove that in a tree with maximum degree $k$, there are at least $k$ leaves

Showing that $U(2^n)$ is not cyclic for $n \ge 3$

Two Circles Can Have At Most One Common Chord? (IMO)

Injection $\mathbb N \times \mathbb N \times \mathbb N \to \mathbb N$

Grandi's series contradiction

But what is a continuous function?

Infinite Cartesian product of countable sets is uncountable

Expected value of rolling dice until getting a $3$

Puzzled by $\lim\limits_{x \to - \infty} \sqrt{x^2+x}-x$

pigeonhole principle clarification

What is the intuition behind the formula for the average?

Prove that $2^n3^{2n}-1$ is always divisible by 17

How to prove $\sum_{n=0}^{\infty} \frac{n^2}{2^n} = 6$?

Integral of a function's derivative does not equal the original function?

Maclaurin Series for $\ln(x+\sqrt{1+x^2})$

Motivation for Jordan Canonical Form

"such that" logical symbol

What is the derivative of $x\sin x$?

Notation used for integrals w.r.t. probability measures

Logarithm of Gaussian function is whether convex or nonconvex?