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12:08 PM
I'm quite shocked to know that even people with higher education can make silly & stupid mistakes.
 
Greetings
 
@Venus Well, that applies to most politicians in the world.
 
Greetings
 
@JasperLoy I said so after reading things about Bill D, Arturo M, and Robin C on meta.
 
$$ \int_0^\infty \frac{t e^{-t}}{(x+t^2)^2}\,\mathrm{d}t $$ ?
 
12:12 PM
They're not politicians, though
 
First, I'd focuse on the integral inside $$-\frac{\partial }{\partial x}\left(\int_0^\infty \frac{t e^{-t}}{(x+t^2)}\,\mathrm{d}t\right)$$
 
@Venus You mean they said stupid things too?
 
This flows pretty naturally by, say, letting $t \mapsto \sqrt{x} t $ and then combining it with the exponential integral. The rest is boring.
 
@JasperLoy Most likely YES, I haven't read the entire posts yet
 
@N3buchadnezzar did you see this one? $$\int_0^{\infty}\left( \frac{\log ^2(\gamma x+1)}{(\gamma x+1)^{\large \sqrt[3]{\log(2)}}}-\frac{\log ^2(\pi x+1)}{(\pi x+1)^{1+\sqrt[3]{\log(2)}}}\right) \frac{1}{x} \, dx=\frac{2}{\log(2)}$$
 
12:21 PM
@Chris'ssis No =)
 
this conversation is over if he is in the room @JasperLoy
The End
 
@N3buchadnezzar You should have received this one in your exam. :-)
 
@Chris'ssis Then I think I would have been thrown out for crying too loud
 
@N3buchadnezzar :D
 
Can someone link or show me a couple of easy limits which can not be computed by l'hôpital?
Talking about precalc / super early higschool.
 
12:26 PM
@N3buchadnezzar Yeah, I can show you. Just think a bit of the exponential function (and not only).
For instance ...
$$\lim_{x\to\infty}\frac{x-\sin(x)}{x+\sin(x)}$$
 
@Chris'ssis Yeah. I know something like $\lim_{x \to \infty} \cfrac{e^{-x} - e^{x}}{e^{-x} + e^{x}}$ works.
 
@N3buchadnezzar Yeap.
Or this one ...
$$\lim_{x\to0} \frac{\displaystyle x^2\sin\left(\frac{1}{x}\right)}{\log(1+x)}$$
 
@Chris'ssis From a glance, that one should be $1$ yeah?
The $x \sin 1/x$ is just one and then one is left with $x/\log(1+x)$.
 
Got a quick set theory question, guys.
 
@N3buchadnezzar Not really.
 
12:37 PM
For $(i)$, I've shown that $x \not\in B$ or $x \not\in C \iff x \in (B \cup C)' \implies x \not\in B \cap C$.
 
@Chris'ssis Zero right. Since $\lim_{x \to 0} x \sin(1/x) = 0$. I messed that up
 
@JasperLoy you have your way of ignoring people and I have mine
 
How would I show the reverse? (That $x \not\in B \cap C \implies x \not\in B$ or $x\not\in C$.)
 
$$\int_0^{\pi/2} \left(\frac{1}{x^2}-\frac{\cot (x)}{x}\right) \, dx$$
 
12:48 PM
$\Huge\stackrel{\odot\odot}{\smile}$ Greetings All
 
hi pal
 
A chameleon; well, that's interesting :D How's it hangin?
 
Hisashiburi dana, @Nick!
 
fine thanks, how are you?
 
@KhallilBenyattou Time is a relative quantity, my friend. A long time for you is a nanosecond for me.
@skullpatrol $\large\stackrel{\Huge \mathfrak{S}}{\text{Weird side up}}$ :D
 
12:51 PM
:D
 
Tis' that time of season I guess.
 
You wizard, @Nick.
 
To be jolly :D
 
@Nick (I don't know if I should be offended or not by that statement.)
 
@KhallilBenyattou Twas not my intention as that wasn't directed to you but if you like being offended, go ahead.
 
12:55 PM
I felt that it wasn't your intention. Don't worry, I'm really passive when it comes to what people say. You can't offend me easily, @Nick. ;-)
 
@KhallilBenyattou You are bad at math :P :p :p
 
(Also, it's 'twas, @Nick.) ^_^
 
@KhallilBenyattou I have a joke about passiveness but it would be inappropriate here. I leave it to your imagination =)
 
I know, @N3. It's no fun if you're already good at math.
:P
 
@KhallilBenyattou ... No, but I leave it your imagination. And so far, Dr.Freud has a lot to say.
 
12:58 PM
Hahahahahaha!
 
@N3buchadnezzar I'm terrible at math. I don't even have the mind to learn.
 
Do we really understand math? Someone once told me that we only get used to it.
 
@N3buchadnezzar This will be always a nice limit in high school $$\lim_{x\to 0} \frac{e^{\sin(x)}-e^{\tan(x)}}{e^{\sin(2x)}-e^{\tan(2x)}}$$ without using Taylor series (the limited expansion form)
 
@KhallilBenyattou It's like understanding language. Do you remember what Juliet said to Romeo from the balcony. Those famous words.. can you recall?
 
Can we use L'Hôpital's rule, @Chris'ssis?
 
1:00 PM
@KhallilBenyattou Use it and let me know if you get the result ...
 
@KhallilBenyattou Easiest way is to incorporate the use of $\displaystyle \lim_{x \to 0} \dfrac{e^x - 1}{x}$
 
@DanielFischer
 
$p : \tilde{G} \to G$ be a covering map with $G$ topological group such that $p$ sends identity to identity. I want to prove that $\tilde{G}$ is also a topological group.
Here's what I thought :
$G$ is a group, so there is a map $G \times G \to G$
 
If $\tilde{G}$ is not assumed a topological group, what does "sends identity to identity" mean?
 
1:07 PM
You can lift this guy to $\tilde{G}$ so there's a map $\tilde{G} \to G \times G$
@DanielFischer Oh yikes I mean a point $\tilde{e}$ is given such that $p(\tilde{e}) = e$, $e$ identity of $G$.
And we have to prove $\tilde{G}$ is a top group with identity being $\tilde{e}$
@DanielFischer Is that clearer?
 
Okay, so you just have a covering of a topological group, and want to show the covering space can also be made a topological group, with an arbitrary element above the identity of $G$ becoming the identity.
 
Yes.
OK, now we have $ G \times G \to \tilde{G}$ by lifting
 
Any further assumptions on the spaces?
 
@DanielFischer path-connected, locally path connected, semilocally yadda yadda yes
 
Okay.
 
1:11 PM
OK, so we have $G \times G \to \tilde{G}$ by map lifting.
 
So the first thing is to think about how you'd define the multiplication.
 
I am thinking abstractly.
$\tilde{G} \times \tilde{G}$ covers $G \times G$.
 
@BalarkaSen How do you know that $G\times G$ is a space of the type that have lifts?
I mean, $S^1\times S^1 \to \mathbb{R}$ doesn't look promising.
 
OK, I dunno if the image fundamental group sits inside the image fundamental group of the cover, yikes.
OK, rethinks
 
It doesn't fall out with L'Hôpital, @Chris'ssis.
 
1:14 PM
@DanielFischer while he is thinking could you please adjust your "ears" :-)
 
@KhallilBenyattou I know that.
 
@Chris'ssis It's 1 right? I was waiting for someone to confirm.
 
For $(i)$, I've shown that $x \not\in B$ or $x \not\in C \iff x \in (B \cup C)' \implies x \not\in B \cap C$.
How would I show the reverse? (That $x \not\in B \cap C \implies x \not\in B$ or $x\not\in C$.)
 
@KhallilBenyattou I'm sorry to ask, but you know I'm an idiot... What is A \ B?
 
The set difference between $A$ and $B$. $A - B$ is the set of all elements in $A$ that aren't in $B$, @Nick.
 
1:19 PM
@KhallilBenyattou Oh, I call that $\Bbb A - \Bbb B$. Apparently, many texts have used $\Bbb A \setminus \Bbb B$
 
Edited! Yep, they are both the same anyway.
 
Well I guess I can commutative diagram outta this.
Blergh.
 
@BalarkaSen Said the titanic to the glacier.
 
Any ideas about the set theory question, @Balarka?
 
I am thinking about covering spaces @Khallil. Can't help.
By the way, @Nick, care to click <- this ping?
 
1:24 PM
@skullpatrol Adjusted, now wait until it updates.
 
@DanielFischer Thank you Spock :-)
 
@BalarkaSen Facebook had a similar feature. I once posted this person is an idiot and for a brief second, I was the centre of hate from all the social circles around me.
 
:P
Well clever of you to hover around the link.
 
@BalarkaSen Actually you wouldn't notice it on the fullscreen IE app on some Win8 machines. Boo hoo for them.
@BalarkaSen: I suck at studying. What's your protip on this matter?
 
@DanielFischer Sanity check : this guy $\tilde{G} \times \tilde{G} \to G$ is not a covering map (it's made out of composing $\tilde{G} \times \tilde{G} \to G \times G$ and $G \times G \to G$), right?
 
1:29 PM
@Nick No.
 
@BalarkaSen Except in trivial cases.
 
yeah, ok.
 
@Chris'ssis Oh god, I've lost my mathematical ability. $\displaystyle e^{\sin x - \sin 2x} = 1$? Right?
 
But trivial groups are, admittedly, not so interesting, topologically.
 
@Nick Yeap.
 
1:32 PM
@Chris'ssis then what is $\dfrac{e^{\sec x} - 1}{x}$ ?
 
@Nick I think you lost your math abilities (maybe temporarily). :-)
 
@Chris'ssis hopefully... but my memory of L'hosp tells me it's $\frac{\mathrm d}{\mathrm d x} (e^{\sec x})$
 
wait i think i got it
 
@Nick $$\lim_{x\to0} \frac{e^{\sin (x)}-e^{\tan (x)}}{e^{\sin (2 x)}-e^{\tan (2 x)}}=\frac{1}{8}$$
 
Pick $(\tilde{g}, \tilde{g}') \in \tilde{G} \times \tilde{G}$
 
1:38 PM
@Venus see above. Some suggestions for an elementary approach?
 
@Chris'ssis Ok, $\displaystyle\lim_{x \to 0} \dfrac{\dfrac{\mathrm d}{\mathrm d x} (e^{\sec x})}{\dfrac{\mathrm d}{\mathrm d x} (e^{\sec 2x})}$ .. mhh, l'hosp doesn't break, why did you say it did?
 
That defines a group operation $\tilde{G} \times \tilde{G} \to \tilde{G}$, @DanielFischer
 
@Nick I didn't say "do it by l'Hopital" at all. I just let @KhallilBenyattou to go that way and see what happens. :-)
 
OK, nevermind.
Gah I need a cup of coffee.
 
@BalarkaSen Ideally, we would want the covering map to be a homomorphism, that would be nicest, wouldn't it?
 
1:42 PM
Well the problem says the multiplication operation is unique and $p$ is a homomorphism, yes.
 
Can someone suggest me a book which has adequate stuff on countability and things like "cardinality of (0,1) and \mathbb{R}". I don't know which category it falls under. Sets?
 
Set theory @SwapnilTripathi
 
@Chris'ssis Ah thanks. Hey, as you see, I'm very rusty on everything at the moment. Can you tell me the best way I can unwind and get back into the flow... I mean you're always in the flow. How do you do that?
 
Book recommendation?
@BalarkaSen
 
@BalarkaSen So, maybe it would be a good idea to look at a small neighbourhood of $\tilde{e}$ first.
 
1:44 PM
No idea. Any basic set theory book has that stuff. @SwapnilTripathi
 
@Nick The best way is to work every day, even a bit. I work pretty hard on this stuff, every day.
 
@BalarkaSen: Thank you! :)
 
Err @DanielFischer I think my lifting approach was right.
The image of $\pi_1(S^1 \times S^1)$ by $S^1 \times S^1 \to S^1$ in $\pi_1(S^1)$ is indeed trivial.
So the lift $S^1 \times S^1 \to \Bbb R$ exists/
 
Yea, @Nick. @Chris'ssis decided to lead me down the garden path with L'Hôpital.
 
@BalarkaSen The image is not trivial, $\mu_\ast (\{1\}\times \operatorname{id}) = [\operatorname{id}]$.
 
1:49 PM
@Chris'ssis and if you tell me that what fuels you is your passion for it, then I am kindly asking you to give me one more reason that makes you tirelessly strive for it.
 
Grr. It's Z.
 
Anyone with no work to do, homework: Finish this list
 
@BalarkaSen But lifting is not a wrong idea, you just need to lift the right things.
 
Oh I think get it
 
@KhallilBenyattou Speaking of Garden paths, those sets questions from earlier. Just use Venn diagrams; most obvious way.
 
1:52 PM
Nope. Venn diagrams don't constitute a rigorous proof, @Nick.
 
I just drew the diagram.
 
@KhallilBenyattou Um yes and no. The written proof comes out from the idea portrayed by what you draw.
 
@Nick I have a huge inner call for this kind of stuff, it's one of those things that make your life complete. I see in what I do very much beauty, a kind of art that feeds my soul and keeps me alive, not just a living dead as many other people we meet every day.
 
@DanielFischer Lift the red marked $\tilde{G} \times \tilde{G} \to G$
 
@BalarkaSen Looks good, now check that it does what you want.
And of course, that you can lift it.
 
1:56 PM
@Chris'ssis When you become really really famous, can I interview you? (This is me booking an appointment for the future)
 
@Nick First, I'd give you a copy of my book for free. :-)
 
@Chris'ssis Sounds like a Rat-Trap
 
@Chris'ssis Don't promise too many free exemplars, you only get a dozen or so usually.
 
@Nick The idea is that I need to publish something to become famous, right? :-)
 
@Chris'ssis eh, I don't mind how you do it. It's a very definite eventuality.
 
2:00 PM
@DanielFischer When are you going to write your book on topological vector spaces?
 
@DanielFischer Well, right. On the other hand, I don't know many people in the real life that would appreciate to receive a copy of my book. :-)
 
@Chris'ssis This is real life too.
 
Hey, @RonGordon is here!
Hello.
 
@BalarkaSen When I don't idle around on the site too much.
 
Well that's going to be hard. You're becoming a mod @Daniel
 
2:01 PM
@Nick I mean they don't understand my passion and the things I do.
 
@Chris'ssis Suggestion for what? I don't see the problem
 
@DanielFischer ... That book's not going to see the light of day, is it?
 
@Venus $$\lim_{x\to0} \frac{e^{\sin (x)}-e^{\tan (x)}}{e^{\sin (2 x)}-e^{\tan (2 x)}}=\frac{1}{8}$$
 
@Venus There is none. It's not really a "problem"
 
@Nick Frankly, I don't know.
 
2:03 PM
@DanielFischer Obscurity is brighter than darkness as I always say.
 
Can't argue with that.
 
@Chris'ssis Why don't you use L'Hospital?
 
@Venus Does it work (from the beginning)?
 
@Chris'ssis Dunno, I haven't tried it yet
Kinda busy now
 
@Venus OK
 
2:08 PM
lol, no has time for 2 + 2 ex machina.
 
Is that a Deus Ex reference, @Nick?
I haven't seen it yet, but it's referred to a lot on the internet. Is it worth watching?
 
Deus ex machina (Latin: [ˈdeus eks ˈmaː.kʰi.naː]: /ˈdeɪ.əs ɛks ˈmɑːkiːnə/ or /ˈdiːəs ɛks ˈmækɨnə/; plural: dei ex machina) from Latin deus, meaning "a god", ex, meaning "from", and machina, meaning "a device, a scaffolding, an artifice", is a calque from Greek ἀπὸ μηχανῆς θεός (apò mēkhanḗs theós), meaning "god from the machine". The term has evolved into a plot device whereby a seemingly unsolvable problem is suddenly and abruptly resolved by the contrived and unexpected intervention of some new event, character, ability or object. Depending on how it is done, it can be intended to move the story...
 
Hello!!! Is there someone that can clarify something at NP-problems??
 
@BalarkaSen Hello!
 
2:17 PM
Nice to see you here @RonGordon
What made you come by?
 
@KhallilBenyattou Aww cheesecake. That's a pretty ........... character. (I'm lost for words. Fill in the blank for me)
 
@BalarkaSen Sometimes I drop in to see what people are talking about. Usually I find people deep into conversations and I have nothing to add, so I leave.
 
I see. I've never seen you here before @RonGordon
 
Don't worry, @RonGordon! Nobody is in deep conversation (about anything math related!). =P
 
@KhallilBenyattou Thanks! What makes you come around to the chat room?
 
2:28 PM
Wait... why did the ChatJax link drop out of the starred posts list??
 
Yikes 15 days are over.
 
Procrastination causes me to come here every day, @RonGordon. ^_^
Not really. It's pretty cool talking about math (especially the stuff I don't understand).
 
Add the spaces around the |, @BalarkaSen!
 
There you go
 
2:31 PM
Thanks!
 
@Balarka @Khalil \o
 
2
Q: Proving $\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx=1-\frac{C}{2}-\ln2$

gcy-rolleNowadays I encounter a integral which is difficult for me to solve it,Please help me to find it.Thank you! $$\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx=1-\frac{C}{2}-\ln2$$ Where C is EulerGamma Constant

 
BTW, anyone remember what all the ChatJax alternatives out there are called? I've been working on yet another one, but I'm pretty sure all the obvious names like ChatJax2 are taken. :/
 
The names of all would be rather a big list I'd guess
ChatJax2 seems not to be in use, according to google
I've got a question. I want to show homeomorphism between the boundry of the unit square, and the unit circle. So I draw the picture and figured out that throwing rays from the center of both outside will meet each at a single points, and forms a continuous open function. But I have no idea how to prove it is injective and bijective
Is it enough to say that for every point on the square, I can send such a ray and it will meet a single point on the circle, and vice versa?
 
2:37 PM
That's the right idea @Studentmath
 
@Venus This is straightforward.
 
Write out the explicit formula.
 
@Chris'ssis Post yours then ^^
 
Hello everyone
 
Hah, $h(x,y)=(x,y)/|(x,y)|$, right?
 
2:39 PM
yes
 
Awesome, thanks!
 
no problem
 
@DanielFischer Have you given any thought as to publishing at all? For example, what sort of typesetting system would you use/are you using?
 
you're doing homeomorphisms @Studentmath?
 
Well, just started
 
2:40 PM
i see. i've got a problem for you.
 
Shoot, I will try it out after these exercises
 
show that a sphere minus a point is homeomorphic to $\Bbb R^2$
 
@Venus $\displaystyle \int_0^{\infty}\frac{x}{(x^2+1)(e^{2\pi{x}}+1)}\mathbb{d}x=1-\frac{C}{2}-\ln2=1-‌​\frac{\gamma}{2}-\ln2$?
Derp, nvm. It says C is the Euler-gamma constant, also known as the Euler-Mascheroni constant
I was right, lol
 
Sphere being the closed ball in $\Bbb R^3$?
 
no, the boundary of the open ball.
 
2:42 PM
Ah, okay
 
@RonGordon I'd use LaTeX. It's sometimes a pain to get it to do what you want, but overall, most stuff is done right straight out of the box, so you only have to wrestle with it on some finer points.
 
@Studentmath you can do this if you think about it hard enough.
your ray approach works, but it needs to fit the situation
 
I will earn the Enthusiast badge in 9 hours and 15 minutes :D
 
0
A: Proving $\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx=1-\frac{\gamma}{2}-\ln2$

Chris's sisHint: make use of the Binet's second formula http://mathworld.wolfram.com/BinetsLogGammaFormulas.html.

 
@Balarka well every sphere minus a point is homeomorphic to a different sphere minus a point
 
2:45 PM
@Venus ^^^
 
@Studentmath ok, that is obvious (rigid motion). so?
 
So it's enough to show it for a specific sphere minus a point (just thinking outloud)
 
oh ok. sure.
 
@Chris'ssis I think you should elaborate your answer because not everyone here understands it including me
 
Oh, I think I got it @Balarka
 
2:48 PM
ah?
 
$\Bbb R^2$ is homeomorphic to $(x_1,y_1,0)$ in $\Bbb R^3$, right?
 
yes
 
So I take the sphere centered at $(0,0,1)$ and consider removing it's top point
 
mmhmm
 
Then from that top point I can send rays down to $(x_1,y_1,0)$, and each ray crosses the sphere once and $(x_1,y_1,0)$ once
 
2:51 PM
yes, that's it.
 
I probably wouldn't have gotten it (that quickly) without the ray hint though :P
 
it's called stereographic projection, for what it's worth.
very important.
 
This very homeomorphism from sphere to $\Bbb R^2$?
 
yes
here's a related exercises : show that boundary of a geometric cone with a circular base in $\Bbb R^3$ is homeomorphic to a disk @Studentmath
 
Well if I send rays from every point at the disk upwards, they hit the cone at a single place - very non-rigurously speaking, right?
 
2:57 PM
?
you realize what i mean by cone do you?
take a cylinder and punch the circular boundary of one side of the cylinder to a point.
 
Yes, the cone you speak of is without it's circular base, right?
Only the boundary
 
eh
that is a cone, @Studentmath
the surface of the object, not the interior.
 
Yeah. The boundary is like the party-hat cone, doesn't have anything below
 
ok, so how do you propose to solve the exercise
 
Take the disk to be the circular base
 
3:01 PM
ok
 
Now from the top of the cone I send a straight ray downwards to the base - that's the height of the cone.
 
ok, sure.
 
Every point on the base I map to the cone by a ray that is parallel to the height
 
ok
yes, that does the trick
 
That will form a bijective and injective function. It is open and continuous - I can look at the basis of the disk - yeah
I have a question though regarding my original question -
 
3:04 PM
@Studentmath *surjective
 
Oh. I could just say bijection though, right?
 
sure
 
Anyhow, $h^{-1}(x,y)=|(x,y)|(x,y)$, right?
 
@Venus what do you get if you differentiate that formula with respect to $z$?
 
your function was $h(z) = z/|z|$
 
3:09 PM
@Chris'ssis I'm trying to evaluate it in other way although I'm not sure it works
 
and then make use of $$\frac{1}{e^x+1}=\frac{1}{e^x-1}-\frac{2}{e^{2x}-1}$$
 
@Studentmath no why should it be that.
 
@Balarka yeah silly mistake
 
you don't need explicit formulas, @Studentmath (although it makes continuity quite obvious)
your ray map is injective
 
I managed with the original $h$, showed it is bijection, open and continuous
 
3:16 PM
(Sorry about the random stars/unstars, folks. My ChatJax replacement script had a bug with starred posts, and I needed to test it. I think it's fixed now.)
 
and construct another map from your unit circle to unit square by taking a point and sliding it through a ray that takes it to the center
your map composed with this map is identity
and this map composed with your map is also identity
there you go @Studentmath.
 
Yes, that'll also work
 
Is my answer good enough now (well, a hint)
0
A: Proving $\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx=1-\frac{\gamma}{2}-\ln2$

Chris's sisHint: make use of the Binet's second formula http://mathworld.wolfram.com/BinetsLogGammaFormulas.html. $$\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx$$ $$=\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}-1)} dx-2\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{4\pi x}-1)} dx$$ $$=\int_{0}^{\infty}\frac{x...

@Venus ^^^
That's all.
Q.E.D.
 
@Huy Was there a point in time where Bill D had gone again?
 
is sub-multiset the right term?
or is it something else?
 
3:23 PM
sure @Lembik. people also use subbag. ugh.
 
interesting.. sub-bag or subbag?
 
sub-bag
 
@BalarkaSen thank you
 
@Venus I have to admit this idea came to mind in the few 5 seconds I showed the question. Just a matter of practice.
I also wonder why I'm not highly upvoted ... maybe I should delete the answer that is not appreciated. :-)
 
@BalarkaSen Do people use the same $A \subset B$ when B is a bag and A is a sub-bag?
@Chris'ssis I think people like full answers more than hints
@Chris'ssis partly because if you not a real expert, it's hard to know if the hint is any good
 
3:29 PM
Wait a minute... Students are taking or already have taken final exams or midterms. Does that mean that homework questions will be few and far between over the holidays?
 
@Chris'ssis I am referring to potential upvoters
 
@Lembik That way is a brilliant way ... and I don't say that because is mine.
 
@Chris'ssis I didn't understand that
"not because is mine." ??
@Chris'ssis you mean your hint is brilliant?
 
@Lembik did you understand that? Well, it looks more like an answer since from that point all is trivial.
 
@Chris'ssis the question is how much effort is a potential upvoter going to put into understand your hint
@Chris'ssis sure the OP should put some effort in. But why should a potential upvoter?
who is not the OP
 
3:33 PM
@Lembik isn't everything very clear at this point???
0
A: Proving $\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx=1-\frac{\gamma}{2}-\ln2$

Chris's sisHint: make use of the Binet's second formula http://mathworld.wolfram.com/BinetsLogGammaFormulas.html. $$\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}+1)} dx$$ $$=\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{2\pi x}-1)} dx-2\int_{0}^{\infty}\frac{x}{(x^2+1)(e^{4\pi x}-1)} dx$$ $$=\int_{0}^{\infty}\frac{x...

 
no :)
 
@Lembik :-(
 
@Chris'ssis there is nothing wrong.. it's just that random passers by are different from people who are interested in that question specifically
and to get upvoters you want to make the random passers by happy
 
@Lembik Yeah, maybe ...
 
Ugh... I still haven't gotten any more upvotes for the awesome answer I posted on my very first question.....
 
3:37 PM
@Chris'ssis I would just finish the answer
but of course it is up to you
 
@Lembik If the person that posted the question wants me do more, I'll do it.
 
@Chris'ssis then you will only get his/her upvote :)
 
@Lembik We'll see. There are many users that I expect from they to understand immediately that hint.
 
@Chris'ssis good luck
 
I mean, seriously... How is it fair that I only got two upvotes for this?
 
3:45 PM
Can I ask what you mean by $\mathbb{d}$ in $\mathbb{d}t$, @teadawg1337?
Also, may I ask which texts you learnt about Polylogarithms from?
 
@teadawg1337 You've 3 upvotes.
 
@Khallil I taught myself the properties of polylogarithms using Wolfram Alpha, and $\mathbb{d}t$ is the same as $dt$, I just prefer to write $\mathbb{d}t$ because it matches my handwriting
I italicize variables when I write out math problems
 
Oh, fair enough. I thought that \mathbb{...} numbers were reserved for sets like $\mathbb{Z}$, $\mathbb{Q}$, $\mathbb{Z}[i]$, $\mathbb{S}$ etc.
 
@Khallil Lowercase letters don't "shift" left in \mathbb
 
What do you mean by 'shift', @teadawg1337? :/
 
3:52 PM
while we are complaining.. why does no one have anything to say about math.stackexchange.com/questions/1059379/… ?
 
@Khallil Uppercase letters kinda look like two of the same letter juxtaposed, with one shifted slightly further away to produce a sort of outline. For example, $\mathbb{Z}$ has a diagonal empty rectangle (sort of) in the middle, but $\mathbb{z}$ does not
 
Yea it does. Choosing $\mathbb{Z}$ and $\mathbb{z}$ is a bad example!
However, I do see what you mean, although it's not entirely correct.
Consider $\mathbb{N}$ and $\mathbb{n}$.
 
I know it's not entirely correct, I'm frustrated that I can't explain this correctly :(
$\mathbb{N}$ is N, but with the middle part not "filled in"
Ugh, I'm so bad at explaining this sort of thing.....
 
The official term is "blackboard bold": en.wikipedia.org/wiki/Blackboard_bold
 

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