Consider functions $f(x)$ defined and real-analytic for $x>0$ , such that
for all real $x,y > 0$ and integer $n > 0$ :
$$ sign (\frac{d^n }{d^n x} f(x) ) = sign (\frac{d^n}{d^n x} f(x+y) ) $$
In other words ; the signs of the derivatives do not change over the positive reals.
Some trivial exa...
From Wikipedia, a linear map (also called a linear mapping, linear transformation or, in some contexts, linear function) is a mapping V → W between two modules (including vector spaces) that preserves (in the sense defined below) the operations of addition and scalar multiplication.
Here $p$ is an odd prime, $n$ is uniform on $[0, 2^\lambda]$, and $\lambda$ is a constant. We define distribution $\mathcal{D}$ by:
$$x \xleftarrow{\$} p-2^\lambda n$$
Assume $p \approx 2^{4\lambda}$, $\lambda \in \{128, 256\}$, and $0 \leq k \leq \log_2 \lambda$. Do a non-negligible fraction of...
I have to answer the following two questions:
Using Zorn's Lemma, one could try to give a "proof" of the following statement: Every subgroup $H$ of a group $G$ such that $H \neq G$ is contained in a maximal subgroup of $G$. Explain why this argument does not work.
Is it true that any group has ...
@ZachHauk Both? Anything similar that piques your interest or might be fun. Granted, money is a typical barrier that one must scale unfortunately, at least for immersive programs like that.
speaking of... I need a solid algebra text. I was supposed to start analysis+algebra last fall, now I'm almost a year behind because of unnecessary pre-reqs and other crap :/
*majority are math majors among the total in the class. perhaps the more diligent math majors are the ones who stayed
mm lemme check
the material is nominally the first chapter of Stoll's introductory RA
prove $p\text{ odd}\;\Leftrightarrow\; p^2\text{ odd}$; prove (by induction) sum of first $n$ positive odd integers is $n^2$; show $[1,3]$ and $[5,8]$ are equivalent by finding a specific bijection; show the set of all positive odd integers is countable by bijecting it with N
what are supremum/infimum of $\{\frac{n+1}{n}\,|\, n\text{ positive integer}\}$? prove or offer counterexample for a) A, B uncountable then A union B uncountable; b) A, B uncountable then A intersect B uncountable; c) x,y irrational then x+y irrational; d) x irrational, y nonzero rational, then xy irrational
You never said whether we're assuming $T:\Bbb C\to\Bbb C$ is $\Bbb C$-linear or $\Bbb R$-linear, but in either case the conclusion is true.
In fact, if $V_1,V_2,W_1,W_2$ are vector spaces and $f_1:V_1\to W_1$ and $f_2:V_2\to W_2$ are linear maps, then $V_1\oplus V_2\to W_1\oplus W_2$ defined by $(v_1,v_2)\mapsto (f_1(v_1),f_2(v_2))$ will also be linear (and is usually called $f_1\oplus f_2$).
We did it with Lagrange multipliers the first time. He said this is vital because he'd use weak compactness of the unit ball to get the infinite dimensional case
There is one thing confuse me, I have a system of ode, $x'=y, y'=-9x$, why I can not write the transformation matrix as $\begin{pmatrix}3i & -3i\\-1 & 1\end{pmatrix}$
@DHMO hmm, since $\omega_1$ is well ordered but has cardinality continuum, perhaps something like a continuum of singletons except there are gaps between thus unlike the reals where it is dense (because $\omega_1$ is well ordered, we are able to always find the next element)?
@DHMO yes I know, but when I built intuition on infinite things, often the first step is I worry about the size first, then consider the ordering and the topology next
@Secret I wanted to make sure that you are aware that a room with no messages of 14 days gets frozen. I am mentioning this in connection with Zero-term algebra chat room. Of course, if a frozen room is needed again, you can ask a moderator to unfreeze it.
@DanielFischer Just for clarification, are you saying that perhaps $$\lim_{N \to \infty} \int_{-y}^{y}\frac{\pi J_{1}(a(N+1/2+it)) \cot(\pi(N+1/2+it)) }{N+1/2+it} \, i \, dt $$ vanishes for $a=1$, but not for, say, $a=7$? That would seem a bit strange.
Ok I need to sketch the graph of $$\sqrt{x}+\sqrt{y}=1$$. Any ideas anyone? On squaring it twice I'm getting the equation of a rotated parabola. I need to remove the $xy$ term and find all the details of the parabola if I square it. Is it possible to roughly sketch it without doing all the rotation and stuff (directly from the first equation)? @DHMO @BalarkaSen
@DHMO yeah. If my intuition is correct, then by cardinal arithmetic, we get $\mathfrak{c}\mathfrak{c}=\mathfrak{c}$ (viewed as a line, there are continuumly many singletons, but each singleton has cardinality continuum), thus giving the excepted and that it is as large as the reals
I have asked a question on the main site on calculus,it seems really tough question,Wolfram alpha fails at this question even with pro time .If anybody is interested then please answer it ...Link -->http://math.stackexchange.com/questions/2161846/just-another-problem-on-integration
What I tried was I took $$\tan^{-1}(x) =t $$ ,but I got terms like $$\cos(\tan(t))$$ which I don't know what to do with,,,
So please guide me into solving this..
@MartinSleziak Thanks, I will let the mods know when I need that unfrozen cause it will be a while before I can return to it as the next phase in the investigation will be non associative algebras that are not lie algebras, which I am still learning about them
@anonymous It might also be reasonable to try something like $x=u+v$, $y=u-v$ (which is basically rotation by angle $\pi/4$, if you add also factor $1/\sqrt2$ because of symmetry.
@DHMO What can I say to that other than "because Stack Exchange decided to allow duplicate usernames"? (And you could ask the same question basically any experienced SE user who is around. Like DHMO.)
@DHMO I have read up about finite subcovers in physics forums. I think I have resolved my [0,1] compact question for now. Otherwise we can continue on discuss about point set topology. In particular I really need to figure out how I can do limit points better in topology
@Secret give me a pair of disjoint open set and closed set that form (a) a closed set and (b) an open set, under the standard topology. And don't give me the empty set
@Secret If you do not mind if I correct you s;s;ogjt;u, it would be more precise to say that the cardinality of real line is $\aleph_1\mathfrak c=\mathfrak c$. But you are right that we get that from $\mathfrak c \le \aleph_1\mathfrak c \le \mathfrak c \mathfrak c = \mathfrak c$.
Anyway, it's easy to derive on your head. If (x, y) rotates to (x', y') by angle theta counterclockwise, then the x-component of x' is x cos(theta) [just do it mentally] and the y-component is y sin(theta).