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Alex's user avatar
Alex's user avatar
Alex
  • Member for 11 years, 7 months
  • Last seen more than a week ago
194 votes

Too old to start math

35 votes

How to prove that $\lim\limits_{x\to0}\frac{\sin x}x=1$?

17 votes

Expectation on 1/X

16 votes
Accepted

What does the value of a probability density function (PDF) at some x indicate?

14 votes

How to determine equation for $\sum_{k=1}^n k^3$

11 votes

Sum of Square roots formula.

10 votes

What is an intuitive approach to solving $\lim_{n\rightarrow\infty}\biggl(\frac{1}{n^2} + \frac{2}{n^2} + \frac{3}{n^2}+\dots+\frac{n}{n^2}\biggr)$?

10 votes
Accepted

What is $\int\frac{dx}{x+\sqrt{1-x^2}}$?

10 votes
Accepted

How do I find the cumulative distribution function of a binomial random variable?

9 votes

Probability of questions being on an exam

9 votes
Accepted

Flip a fair coin until three consecutive heads or tails appear

9 votes

Approximate $\sqrt{e}$ by hand

8 votes

How do I find $\lim_{x\rightarrow \infty} x\sin \frac {c}{x}$?

8 votes

How to derive the closed form of the sum of $kr^k$

8 votes

When is a Markov chain null recurrent?

8 votes

How to differentiate $y=\sqrt{\frac{1+x}{1-x}}$?

8 votes

Linear combination of independent poisson random variables

7 votes
Accepted

Find the values of α and β for which this series converges.

7 votes

How many distinct permutations of the string "NADAMADRID" have the word DAM appearing in them?

7 votes

How to compute $\sum_{n=1}^\infty{\frac{n}{(2n+1)!}}$?

7 votes
Accepted

Binomial theorem for non integers ? O_o ??

7 votes

Find $\lim\limits_{x \to \infty} \left(\sqrt{x^2+x+1} - \sqrt{x^2-x} \right)$

7 votes

Infinite sum of logarithms

7 votes

If $\sum a_n$ with $a_n>0$ is convergent, then is $\sum {a_n}^2$ and $\sum \sqrt{a_n}$ always convergent?

6 votes
Accepted

Why is the expected number coin tosses to get $HTH$ is $10$?

6 votes

Calculate $\sum_{k=1}^n \frac 1 {(k+1)(k+2)}$

6 votes

Collection of surprising identities and equations.

6 votes
Accepted

Solving a recurrence relation, $a_n = \sqrt{n(n+1)}a_{n-1} + n!(n+1)^{3/2}$

6 votes
Accepted

Calculate limit with summation index in formula

6 votes
Accepted

When can I cancel out a differentiation and integration operation?

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