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Jun
16
comment Spectral Measures: Uniqueness
@Freeze_S Thanks, but no, I didn't deserve it.
Jun
16
comment Spectral Measures: Uniqueness
@Freeze_S I don't need really reference. I was just wondering. For example, Birman and Solomyak have some nice books about it. I know also that in Rudin (Function Analysis) we can find also some stuff, but not too much.
Jun
16
comment Spectral Measures: Uniqueness
Hi, just wondering, from which book are you learning stuff about spectral measure?
Jun
4
comment Estimate for the power of a integral
Look at en.wikipedia.org/wiki/…
May
27
reviewed Approve What is corresponding Lie group for Lie algebra of vector fields in dynamical systems?
May
27
reviewed Approve How to find the area of the triangle formed by the lines $y=ax$ , $x+y-a=0$ and the $y$ axis?
May
27
comment $\frac{1}{{1 + {\left\| A \right\|} }} \le {\left\| {{{(I - A)}^{ - 1}}} \right\|}$
Hi, is $||| \cdot |||$ unitarily invariant norm or?
May
22
revised How to evaluate this indefinite integration $\int \frac{\tan^4 \theta d \theta}{1-\tan^2 \theta}$?
added 18 characters in body
May
22
comment use parseval's identity to evaluate the integral $ \int_{-\pi}^{\pi}\sin^4 xdx$
Call me crazy, but I would wrote that in reverse order, that is $\pi \cdot \frac{1}{4} + ...$, because $a_0=\frac{1}{2}$. I mean, your answer is correct, but... That just me. And oh, yes, answer is $3\pi/4$, or?
May
22
comment Feynman technique of integration for $\int^\infty_0 \exp\left(\frac{-x^2}{y^2}-y^2\right) dx$
Just for note: There is similar, but harder problem, when you have $dy$ instead of $dx$. If you want to solve that problem (where $x$ is parameter, say $x>0$ (but you can do all for $x \in \mathbb{R}$)), first find $I'(x)$ and then use substitution $y \mapsto \frac{x}{t}$ for $I(x)$, where $I(x)$ is your integral. You should end with something like $I'(x)+2I(x)=0$, that is $I(x)=Ce^{-2x}$ (you can find that $C=\frac{\sqrt{\pi}}{2}$ from $I(0)=\lim_{x \to 0^+} I(x)$).
May
6
answered Show that holomorphic function $f: \mathbb{C} \rightarrow \mathbb{C}$ is constant
Apr
25
reviewed Approve Is the $C^0$-fine topology finer than the metric topology?
Apr
2
reviewed Approve In $P^n$(projection of $C^{n+1}$) is a variety isomorphic to $P^1$ irreducible?
Mar
30
reviewed Approve how to calculate what I need for final exam
Jan
26
comment Show that if $v\in (V_c)^{\perp}$ then $(Av)\in (V_c)^{\perp}$ for a normal matrix $A$ with an eigenvalue $c$
$\langle x, Av \rangle = \langle x, v c \rangle = ....$
Jan
25
reviewed Approve Bounding summations
Jan
23
awarded  Good Question
Jan
21
reviewed Approve Evaluating the limit $\displaystyle \lim _{x\to \infty }\frac{(x^2+1)}{(x-1)}\sin(\frac{1}{x})$
Jan
17
reviewed Reject What is the intuition behind the exponential distribution?
Jan
15
comment Proving compactness of an operator
You can use ideas from this question math.stackexchange.com/questions/320751/….