2,120 reputation
21446
bio website anhhuy.ch
location Switzerland
age 22
visits member for 4 years, 1 month
seen 3 hours ago

My name is Anh Huy Truong and I am currently studying mathematics at the ETH Zürich.


Dec
17
answered What are some applications of elementary linear algebra outside of math?
Dec
16
answered Is $g$ the unique function with this property?
Dec
16
comment Why is the axiom of choice not taught from the start to mathematics undergraduates?
Every lecturer in my first year courses explicitly stated that they were using the axiom of choice, so I think it depends on the lecturer/university?
Dec
15
reviewed Reviewed Finding a limit using change of variable- how come it works?
Dec
15
reviewed Reviewed Example of finite ring which is not a Bézout ring
Dec
15
reviewed Reviewed Double angle sine
Dec
15
reviewed Reviewed Self-Learning Geometry
Dec
15
reviewed Reviewed Complex Analysis using derivatives
Dec
15
reviewed Reviewed Proofs involving positive real numbers
Dec
15
reviewed Reviewed Complex Analysis using derivatives
Dec
15
reviewed Reviewed Prove Euler's Theorem when the integers are not relatively prime
Dec
15
reviewed Reviewed Metric Geometry determining fixed points
Dec
15
awarded  Custodian
Dec
15
reviewed Reviewed Theorem with seemingly reduntant part
Dec
9
comment A question about surjective functions.
I did use comments to point out what I disagree about. If you have only seen the use of $f^{-1}$ in the sense of the inverse function, I suggest you look up the "preimage" of a function.
Dec
9
comment A question about surjective functions.
I downvoted because I disagree with your answer.
Dec
9
comment A question about surjective functions.
OP is looking for a surjective function f such that $f^{−1}(f(A))\neq A$. Only applied to sets, the use $f^{-1}(Y):=\{x\in X|f(x)\in Y\}$ is rather popular.
Dec
9
comment A question about surjective functions.
I think it might be a bit pedantic but @Leox never explicitly said that $f^{-1}(x) = \sqrt{x}$ is supposed to be the inverse function of $f(x)$.
Dec
9
awarded  Caucus
Dec
5
comment A simple way to evaluate $\int_{-a}^a \frac{x^2}{x^4+1} \, \mathrm dx$?
@Venus: To evaluate $\int_{-\infty}^\infty \cos(x^2) \, \mathrm dx$, substitute $t = x^2$ and use $t^{-1/2} = \pi^{-1/2} \int_{-\infty}^\infty e^{-tu^2} \, \mathrm du$. Then use Fubini's theorem.