Inglese
Du iu spik inglish? Se lo scrivi così, forse hai bisogno di aiuto...
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In evidenza
I have always been out of this section, because I was not up to face the problems I read.
Actually I would like some foreing friends to visit us.
So I thought of proposing an exercise suitable for a student who has just terminated liceo.
Find the smallest real number $a>1$ that satisfies
$\frac{a+sinx}{a+siny}<=e^(y-x)\quad\quad\quad forall x<=y$
Bye, and let me know if my english was bad, I do not want to make a bad impression
Define for which $alpha in RR $ may exist solution in $L^1(RR) $ of the equation:
$y+alpha y$*$e^(-x^2) =f $, being $f in L^1(RR) $ assigned ,$ dot f inL^1(RR)$ [$dot f $ means Fourier transform of $f $ and * means convolution].
Express $y $ in integral form
Hello people! I've got a dramatic work to do: write down the complete list of the mathematics topics I've learnt in last two years. Given that I'm at secondary school, as you can imagine, my English is very poor in the field and I've just a short time to complete the work.
Is there anybody who can suggest me a link with a sort of maths dictionary or, maybe, provide me a proper translation of some expressions? I tried to do it by using Wikipedia, but it takes too long...
Solve the Cauchy problem
$u''+ cu =f(x) ; x> 0 $
$u(0)=u'(0)=0 $
being $c ne 0 $.
Solve the Cauchy problem :
$u''(x)+2u'(x)+2u(x) = f(x) $ , for $ x> 0$
$u(0)=u'(0) =0 $ .
Show that
$((n),(k))=(n!)/(k!(n-k)!)<=2^(n*H(k/n))$
where $H$ is the entropy function:
$H(x)=-xlog_2x-(1-x)log_2(1-x)$.
Let
$x(t) = {([t], t>0),(0, t<0):}$
Calculate Laplace transform of $x(t)$.
After the discussions on bilateral/unilateral Laplace Transforms, I made a brief enquiry on how this topic is treated in the literature , observing how different authors handle the matter.
Do they consider " by default " the unilateral or bilateral transform ?
Furtherly : how non mathematicians approach the Laplace transform and how explain its applications in technical fields such as, for instance, the Telecom world ?
Herebelow you can find how some authors deal with the ...
Let $a<b in RR$.
It's known that each $K in C([a,b]^2)$ can be used to define a compact linear operator $T$ of $L^p([a,b])$ into $L^q([a,b])$ (with $p,q in ]1,+oo[$ s.t. $1/p+1/q=1$) by putting:
(*) $quad AAu in L^p([a,b]), quad Tu(x)=\int_a^bK(x,y)*u(y)" d"y quad$,
where $"d"y$ stands for the standard Lebesgue measure on $[a,b]$. (No need to proof; it's just a prerequisite.)
On the other hand, once assigned a linear differential operator of the second order ...
Determine the solution $u in L^2(RR)$ of the integral equation :
$ u(x)-1/4 int_(-oo)^(+oo) e^(-|x-y|) u(y)dy =xe^(-|x|) $ .
Solve the following equation :
$u'(x)-u(x)+2u$*$e^x = 0 $ ; $ x> 0 $ ( * means convolution.)
Feel free to use the method you prefer
Solve the equation :
$y+e^(-|x|)$*$y = e^(-|x| )$ . (* means convolution ).
Scusate se scrivo in italiano, poiché devo parlare di errori in inglese è meglio che non comincio io a scrivere male.
Voi che siete appassionati della lingua anglo-americana,
che ne pensate dei cosiddetti errori presenti nella traccia di inglese assegnata dal ministero all'esame di maturità per l'indirizzo turistico? Avete seguito la storia sui giornali?
ragazzi ke mi traduce questo brano?io l'ho provato a tradurre cn il traduttore ma nn si capisce nnt...ki ne sà un pò di inglese e kn l traduttore riesce a far uscire qlk di buono?...anke se me lo fate domani nn c'è problema..mi devo fa interrogà..guè..grazie raga
THE CHAIN OF BEING(LA CATENA DELL'ESSERE).
The tudors and olso the Elizabethans had conception of the iuniversal order based on a medieval word-view.The universal order had three main forms:a chain,a series of corresponding ...
Let $X$ be a Banach space and $X'$ its dual. Let ${x_n}\subset X$ weak convergent to $x$ and ${f_m}\subset X'$ weax* convergent to $f$. Is it true that $f_n(x_n)\rightarrow f(x)$?
Solve the equation :
$ f(x) = Phi(x) +lambda* int_0^1 xy f(y)dy $ , where
$Phi(x)$ is a continuous known function, while $ f(x) $ is the unknown function (continuous).
Find all solutions $G=G(x) $ of the differential equation
$G' +a(x) G = delta $
with $ a(x) in C^(oo)(RR) $ .
Let $l^1={x=(x_n) subseteq RR:quad \sum_(n=1)^(+oo)|x_n|<+oo}$, $c_0={y=(y_n)subset RR:quad lim_n y_n=0}$ and $l^oo={x^**=(x_n^**) subset RR:quad "sup"_(n in NN) |x_n^**| <+oo}$.
The two sets of real sequences $l^1, c_0$ turn out to be Banach spaces with their canonical real vector space structure and the norms defined by:
$AA x in l^1,quad ||x||_1=\sum_(n=1)^(+oo)|x_n|$,
$AA y in c_0,quad ||y||_oo="sup"_(n in NN) |y_n|$.
The normed duals $(l^1)^**$ and $(c_0)^**$ are, respectively, $(l^oo,||\cdot ||_oo)$ (the $oo$-norm is the one defined above) and $(l^1,||\cdot ||_1)$: their both Banach spaces.
(No need to proof; we recall ...
Let $X = L^2(RR)$ be the Hilbert $CC$-space of the complex-valued functions that are a.e. defined and Lebesgue square-integrable on $RR$, equipped with the standard inner product $X$ x $X \to CC: (f,g) \to \int_{-\infty}^{+\infty} f(x) g^\star (x) dx$, where $z^\star = $Re$(z) - i\cdot$Im$(z)$, for any $z \in CC$. Then consider the linear operator $F(\cdot): X \to X: f(\cdot) \to \int_{-\infty}^\infty e^{-2i\pi \omega x} f(x) dx$.
THE PROBLEM: is $F(\cdot)$ compact? Can you describe its point spectrum?
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