7,029 reputation
21043
bio website
location Besançon, France
age 34
visits member for 1 year, 11 months
seen 15 mins ago

Mathematics is a hobby for me, and MSE helps me not to forget too much what I learned in university (MS in applied mathematics at Lyon 1). I like especially real and complex analysis, trigonometry, numerical analysis, finite groups theory, number theory and combinatorics. I am not allergic to other fields.

Contact: arbautjc at gmail dot com


14m
answered How to find the integral of cosin function with abs
27m
reviewed Leave Closed How can I compare two bivariate functions
28m
reviewed Close Finding a minimum weight spanning tree?
29m
reviewed Close How to find the covariance of sample mean and sample variance Cov(Xn_bar,Sn2)?
29m
reviewed Leave Open What is a everyday example of a non measurable set?
29m
reviewed Leave Open How many digits of $\pi$ are currently known?
30m
reviewed Close Proving that a function is injective
30m
reviewed Close Two definations of the dynkin system.
30m
reviewed Close Representation of a linear functional
31m
reviewed Approve suggested edit on # of ways to place books on shelf
31m
reviewed Reject suggested edit on Calculate the derivative of sin5x using limits
3h
comment Definition of Functional Limits and Isolated Points
In France the limit is usually defined with only $d(x,p)<\delta$, and not $0<d(x,p)<\delta$ (with the latter it is called "limite épointée").
3h
comment Exercise in number theory
@Ja͢ck The point is to use the (a) to solve (b). The inequality is equivalent to prove that there are at least $\sqrt{N}$ squarefree numbers below $N$.
4h
comment How many circles with radius $r_1$ can be inscribed in circle with radius $r_2$
You mean the maximum number of circles that can be inscribed together, I suppose. Difficult problem, see Circle packing and Circle packing in a circle on Wikipedia.
4h
comment Fourier series for a non-periodic function
@Joseph If $f$ is periodic and has a finite number of discontinuities on any interval, then since $\Bbb R$ is an interval, it must have no discontinuities at all. The correct statement is "a finite number of discontinuities on any bounded interval".
4h
comment Fourier series for a non-periodic function
@Joseph Don't trust Wikipedia too much (see comment above).
4h
comment Fourier series for a non-periodic function
@MattL. I edited the Wiki page, as the statement is obviously wrong. Notice $\Bbb R$ is an interval.
4h
reviewed Reject suggested edit on What function is on the graph?
4h
reviewed Approve suggested edit on Find the general solution to differential equation
4h
reviewed Close Every subgroup H of a group G is a union of cyclic subgroups of G.