584 reputation
1618
bio website
location Taipei City, Taiwan
age
visits member for 2 years, 11 months
seen 1 hour ago

胡皓

I am a retired software engineer.


Jul
19
comment Differential equations,x[t] is periodic
This question is cross-posted on Mathoverflow.
Jul
9
reviewed No Action Needed Comparison test involiving e
Jul
9
comment Are NSA Mathematicians second-rate?
Actually, I am hoping NSA mathematicians would read this question and give us answers. They should have a chance to defend themselves.
Jul
2
awarded  Curious
Jun
19
reviewed No Action Needed How to perform a monotonic function fitting of data points?
Mar
15
awarded  Popular Question
Jan
21
comment Largest white rectangle on board
Cross posted on CS.SE
Dec
25
comment Nonempty subset H of group G is subgroup iff $ab^{-1} \in H $ for any $a,b \in H$
You should put a comment under @Quimey's answer to ask him your question. The OP already know why $b^{-1} \in H$, see his question.
Dec
19
comment Maths at university
@user1729 I mean basic level.
Dec
19
comment Maths at university
@user1729 I am incoporating your comment into my answer. I do mean basic level. You don't expect first year undergrad math student becoming an expert in set theory and logician in a year, do you?
Dec
19
revised Maths at university
added 15 characters in body
Dec
19
comment Maths at university
@user1729 I actually study group theory, too. My reasoning is that you cannot be a good group theorist without knowing set theory. Remember the OP is just starting undergrad math.
Dec
19
answered Maths at university
Dec
6
comment Routing Automaton
@ArthurFischer I am not sure the routing automata here is different from synchronizable DFA in Exercise 1.59 of Sipser's book. If they are the same, I think this is a homework problem.
Dec
6
comment Routing Automaton
What does it mean by $\to^*$ ? If $M$ is deterministic, there is only one $q'$ such that $\delta (q,w) = q'$. What do you mean by individual?
Dec
5
comment Is there a finite commutative semigroup $S$ with $S^2 = S$ which is not a monoid?
What do you mean by $S^2$ ? $SS$ ? I thought $SS = S$ means the binary operation is closed.
Nov
14
comment use induction to prove that $Y_m$ = $X_{m-1}$ is true
What is the difference between this question and the other question proof by induction the following numbers are equal ?
Nov
11
awarded  Civic Duty
Nov
2
comment What is the most concise mathematical expression?
@copper.hat I upvoted both of yours and this. I actually like yours better. $e^{-i\pi}$ would be less concise.
Oct
4
awarded  Yearling