Reputation
5,547
Top tag
Next privilege 10,000 Rep.
Access moderator tools
Badges
1 11 37
Newest
 Good Answer
Impact
~182k people reached

Dec
27
reviewed Approve Definition of exact sequence
Dec
22
comment Does there exist a neighborhood around a real number on the real line whose complement is finite?
As for existence: The topological space being defined is given as the space where the closed sets are the finite sets and the whole space, or equivalently, the open sets are the co-finite sets and the empty set. This is a topology: - The empty set is finite, hence closed, and the whole space has finite complement. - If you intersect arbitrarily many finite sets, the result is still finite. Equivalently, taking the union of arbitrarily many co-finite sets gives you a co-finite set. - The union of two finite sets is finite, and hence, the intersection of two co-finite sets is co-finite.
Dec
22
comment Combinatorial argument for an identity
Hi, two things: 1. What have you tried so far? Have you noticed the connection to "$x_1 + \ldots + x_n \le n$"? 2. The notation "${}^n C_r$" is very outdated; in general, prefer writing $\binom{n}{r}$.
Dec
21
reviewed Approve sequences-and-series tag wiki excerpt
Dec
12
reviewed Approve Problem using the AM-GM inequality
Dec
12
reviewed Approve analysis tag wiki
Nov
24
reviewed Approve Forecasting multiple data sets - mean and standard deviation
Nov
22
reviewed Approve How many integers between $10000$ and $99999$, inclusive, are divisible by $3$ or $5$ or $7?$
Nov
22
reviewed Approve Determine if point is in the 2D square/triangle
Nov
21
reviewed Approve Determine the value of $x$ that is for $x^3-6x+7=0$ is false such that $x\in\mathbb{R}$
Nov
17
reviewed Approve Range of Influence of the Wave Equation?
Nov
14
reviewed Leave Open Lie algebra of the invertible morphisms of a Lie algebra.
Nov
14
reviewed Leave Open Why is the Fourier transform self-inverse?
Nov
14
reviewed Approve All the spaces which are Hausdorff and semi metric spaces, are necesarily metric spaces?
Nov
14
reviewed Approve How do you calculate the wife's age?
Nov
14
reviewed Approve The probability that $n$ items out of $m$ selected turn out to be of a particular kind
Nov
14
comment What is $dx$ in integration?
@Aerovistae: The $\Delta x$ describes the difference between consecutive values of $x$.
Jun
14
awarded  Good Answer
May
17
reviewed Reject Finitely generated modules, related to the Gaussian integers
May
2
reviewed Approve Calculation of Integral of $ \int \sqrt{\sec 2x-1}\;dx$ and $ \int \sqrt{\sec 2x+1}\;dx$