Reputation
Next tag badge:
992/1000 score
280/200 answers
Badges
27 289 583
Newest
 Enlightened
Impact
~4.4m people reached

11h
comment What is the derivative of $\arcsin(x/4)$?
You did nothing wrong: the two expressions are equal.
11h
comment Explanation of exam question on what looks like the handshake lemma.
@niobe: You’re welcome.
11h
answered Explanation of exam question on what looks like the handshake lemma.
11h
answered Help with Discrete Structures proof
12h
comment Proof Bell-Number $B(n+1)=\sum\limits_{i=0}^n\binom{n}{i}B(i)$
It looks fine to me.
12h
answered How to prove that every Paracompact space with the Suslin property is Lindelof
13h
comment Separable iff Lindelof for pseudometric spaces
@Chris: My pleasure!
13h
comment Separable iff Lindelof for pseudometric spaces
@Chris: You’re welcome. Let $\mathscr{U}$ be an open cover of $X$, let $\mathscr{B}$ be a countable base, and let $$\mathscr{B}_0=\{B\in\mathscr{B}:\exists U\in\mathscr{U}(B\subseteq U)\}\;;$$ clearly $\mathscr{B}_0$ is a countable open cover of $X$ refining $\mathscr{U}$. For each $B\in\mathscr{B}_0$ pick a $U_B\in\mathscr{U}$ such that $B\subseteq U_B$, and let $\mathscr{U}_0=\{U_B:B\in\mathscr{B}_0\}$; show that $\mathscr{U}_0$ is a countable subcover of $\mathscr{U}$.
15h
answered Separable iff Lindelof for pseudometric spaces
15h
comment The infinite series $\sum_i a_i \prod_{j=0}^{i - 1}(1 - a_j)$ has sum equal to $1$
@user242758: You’re welcome; glad it helped.
19h
comment How many pairs of adjacent bits?
@MSHossain: You're welcome.
1d
revised How many pairs of adjacent bits?
added 816 characters in body
1d
comment How many pairs of adjacent bits?
@Michael: Take a look now; I think that I got everything straightened out.
1d
revised How many pairs of adjacent bits?
deleted 89 characters in body
1d
answered How many pairs of adjacent bits?
1d
revised How many pairs of adjacent bits?
Added MathJax, clarified statement.
2d
comment How to prove $\sum\limits_{i=0}^n (-1)^i \binom{n}{i} \binom{n-i}{k}=0$
@Barry: I mentally inverted what was happening; it should be okay now. Thanks for drawing my attention to it.
2d
revised How to prove $\sum\limits_{i=0}^n (-1)^i \binom{n}{i} \binom{n-i}{k}=0$
added 138 characters in body
2d
comment What is this semi-circular symbol in the middle of a formula?
A bit more context would help: what are $a$ and $tr_P$? (The symbol often indicates a concatenation of strings.)
2d
answered How to prove $\sum\limits_{i=0}^n (-1)^i \binom{n}{i} \binom{n-i}{k}=0$