@robjohn I like this form much more $$\lim_{n\to\infty} \frac{1}{n^2} \int_0^{\pi/2} \left(\sum_{k=-n}^{n} e^{\large 2k x i}\right)^3 \psi^{(-2)} (x+1) \ dx=\frac{3\pi}{4} \log(2\pi)$$
Sometimes it happens that the image of the function in the plane has $f(x+\pi) = -f(x)$, so the images of $f$ on $[0,\pi]$ and on $[\pi, 2\pi]$ overlap.
There was some discussion of this recently in connection with why $r = \sin n\theta$ has $n$ leaves when $n$ is odd, but $2n$ leaves when $n$ is even.
In polar coordinates $(r, \theta)$, the equation $$r = \sin\left(a \theta\right)$$ gives a rose with $a$ petals if $a$ is odd, or $2a$ petals if $a$ is even.
Thus, the number of petals generated for some values of $a$ are
a | petals
=======+========
1 | 1
2 | 4
3 | 3
...
(The answer to the $r=\sin n\theta$ thing is that when $n$ is odd, it also has $2n$ leaves, but the leaves overlap in pairs, so you can only see $n$ of them.)
Okay, I'm plotting limacons... functions in the form r=acost or r=a(b+c cost) where cos is replacable with sin... does the overlap occur for all such functions?
For $r = a\cos t$ that's exactly what is happening there. Notice that you have $r(t+\pi) = -r(t)$ just as I said a minute ago. For $r = a(b+c\cos t)$ I will have to ponder a little more.
How do I tell W|A to plot theta only between -pi/2 and pi/2?
I rather suspect that W|A is not doing what you think it is regarding the limit on theta. What if it were ignoring the [-pi/2, pi/2]? Then you would see the same result for both ranges.
In fact, that is exactly what it is doing.
Notice that it says it is plotting cos x, not cos t.
Now look at this screenshot, which tries to get it to plot t over a very small interval from -0.00001 to 0. Obviously it is ignoring that request and plotting the whole thing anyway.
@Chris'ssis I was looking at one of your answers and I want to ask you if your geometrical method for evaluating $\int_1^e \ln x\space \mathrm{dx} can be used for limits other than $1$ and $e$ or does it only work for these limits?
oops
$\int_1^e \ln x\space \mathrm{dx}$
@Chris'ssis does ur geometrical method only work for these limits?
@hb20007 There are some nice examples where the geometrical method works great. If I'm not wrong, there is a nice one given on a Harvard-MIT contest, but I need to find it.
@Chris's sis, is it $\frac{\pi -2}{2}$ ? -- also, I can't seem to find the series you posted a week ago (I was going to take another crack at it now that I've brushed up on double series) -- could you repost it (or post another one like it)?
@Chris'ssis is the area between a function and the x-axis within certain limits (x=a, x=b) always equivalent to the area between its inverse and the y axis between y=a, y=b?
@Chris'ssis I did. I got the answer to the second integral you gave me using your geometrical method which works very nicely but I had to assume that the thing I asked you holds true (it always does, right?)
@hb20007 well, you have there $(x=0, x=1)$ and $(y=0, y=\pi/2)$ that means you have different limits. It depends on how you choose the limits. That's why I told you to make a drawing.
@Chris'ssis True. But by drawing a rectangle with height $\pi/2$ and width $1$, I was able to get the area required by minusing the area of the rectangle by the area between the inverse sin curve and the y axis, which I assumed to be the integral of sinx betwen $(x=0, x=1)$
And, he is one of the very few people who surpass Ramanujan, @Chris'ssis. Such a person with vast knowledge on several branches of mathematics is rarely seen.
@Chris'ssis Yes. Thank you... This is really cool. Can I apply my 'assumption' to other questions or is it by chance that the area between the inverse curve and the y axis is the same as the area between the 'actual' curve and the x axis within the same limits on each respective axis?
@G.T.R Yes, I think so. That's because of the fact that Ramanujan is the founder of modern algebraic number theory and Tao is the founder of modern combinatorial number theory.
In every field there's always that person who's just years ahead of their time. For instance, Paul Morphy (born 1837) is said to have retired from chess because he found no one to match his technique that very much resembles modern chess theory.
So, who were the Paul Morphys of mathematics?
We could argue Raj did not stand on the shoulders of giants, since he was secluded from mainstream mathematicians when he independently came up with his work
@BalarkaSen Well, that "god" you don't need to take it literally, but it's just a way of expression the fact that he was exceptionally awesome in all he did.
@DanielFischer I'm trying a new approach of posting answers as quickly as possible. This led to a bunch of typos in that answer I posted earlier. I much prefer taking my time. But then the types of questions I can answer are limited.
@RandomVariable Don't sell yourself for less than you're worth. And find a compromise between being quick and typo-free that you're comfortable with, it's not worth stressing out just because maybe Ron Gordon types faster than you.
It's this one $$\lim_{n\to\infty} \left(\frac{1}{\displaystyle \binom{2014}{2014}}+\frac{1}{\displaystyle \binom{2014+1}{2014}}+\cdots+\frac{1}{\displaystyle \binom{2014+n}{2014}}\right)$$
@Chris'ssis let $n$ be a positive integer and let $a_1,a_2\dots a_n\in \mathbb R$ with $a_1+a_2\dots a_k\leq k$ for $k=1,2\dots n$ prove $\frac{a_1}{1}+\frac{a_2}{2}\dots\frac{a_n}{n}\leq \frac{1}{1}+\frac{1}{2}\dots \frac{1}{n}$
@DanielFischer I incorrectly stated that my internet connection at home is 6 Mbps. It's actually half that. So we're basically in the same boat. I actually prefer watching videos on my phone since the connection is so much faster.
I am having a problem with the derivation of the prolongation formula from PJ Olver's text :"Applications of Lie groups to differential equations" Page 105,106.
Considering a differential equation with independent variable(x) and one dependent variable(u).
(x,u) $\subset$ $X \times U$
The fir...
@Bananarama Thanks for the question. It's a cute one. Right now I'm working on $$\int_0^{\pi/2} \int_0^{\pi/4} \frac{\sin^2(x y)}{y \sin^2(x)\sin(\pi y) } \ dy \ dx=\log\left(\frac{\displaystyle 2\Gamma\left(1+\frac{\pi}{8}\right)\sqrt{\frac{2}{\pi}\cdot \tan\left(\frac{\pi^2}{8}\right)}}{\displaystyle \Gamma\left(\frac{1}{2}+\frac{\pi}{8}\right)}\right)$$ that I created today. I try a second solution.