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Did
  • Member for 13 years, 4 months
  • Last seen more than 5 years ago
1007 votes

Construct a function which is continuous in $[1,5]$ but not differentiable at $2, 3, 4$

248 votes
Accepted

How to define a bijection between $(0,1)$ and $(0,1]$?

191 votes

Evaluating $\lim\limits_{n\to\infty} e^{-n} \sum\limits_{k=0}^{n} \frac{n^k}{k!}$

182 votes

$1=2$ | Continued fraction fallacy

164 votes
Accepted

Compute $ \lim\limits_{n \to \infty }\sin \sin \dots\sin n$

132 votes
Accepted

Expected time to roll all $1$ through $6$ on a die

79 votes

Find closed form for $1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 10, 10, \ldots$

75 votes
Accepted

Enumerations of the rationals with summable gaps $(q_i-q_{i-1})^2$

73 votes
Accepted

Is there a name for the function $\max(x, 0)$?

71 votes

Can a coin with an unknown bias be treated as fair?

64 votes
Accepted

Why does the median minimize $E(|X-c|)$?

61 votes

Fermat's Last Theorem (Case n = 3) Question

57 votes
Accepted

What is the proof that covariance matrices are always semi-definite?

56 votes
Accepted

Order statistics of i.i.d. exponentially distributed sample

56 votes
Accepted

Explain why $E(X) = \int_0^\infty (1-F_X (t)) \, dt$ for every nonnegative random variable $X$

56 votes
Accepted

Expected value of maximum of two random variables from uniform distribution

55 votes
Accepted

If a function has a finite limit at infinity, does that imply its derivative goes to zero?

54 votes
Accepted

De Morgan's law on infinite unions and intersections

52 votes
Accepted

How to deduce the CDF of $W=I^2R$ from the PDFs of $I$ and $R$ independent

51 votes

Summing the power series $\sum\limits_{n=0}^\infty (-1)^n \frac{x^{2n+1}}{2n+1}\prod\limits_{k=1}^n\frac{2k-1}{2k} $

51 votes

Are Monotone functions Borel Measurable?

50 votes

What's the probability that a sequence of coin flips never has twice as many heads as tails?

47 votes

Solve $x\sqrt{x\sqrt{x\sqrt{x\dots}}} = 4$

46 votes
Accepted

Summing (0,1) uniform random variables up to 1

45 votes
Accepted

How to compute the series $\sum\limits_{x=0}^\infty\sum\limits_{y=0}^\infty\sum\limits_{z=0}^\infty\frac{1}{2^x(2^{x+y}+2^{x+z}+2^{z+y})}$

44 votes
Accepted

Difference between logarithm of an expectation value and expectation value of a logarithm

41 votes

Evaluating $\lim\limits_{n\to\infty} \left(\frac{1^p+2^p+3^p + \cdots + n^p}{n^p} - \frac{n}{p+1}\right)$

41 votes

Function on $[a,b]$ that satisfies a Hölder condition of order $\alpha > 1 $ is constant

38 votes
Accepted

Why left continuity does not hold in general for cumulative distribution functions?

38 votes
Accepted

Unbiased Estimator for a Uniform Variable Support

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