Calc Problem about a Racetrack

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Homework Statement


Alright, so I have this problem from a textbook I'm using:

There is a track (of unit length) with ##k## runners on it. At the time ##t=0##, the runners start from the same position and take off simultaneously. Each runner has a distinct speed. A runner is said to be "lonely," at a time ##t##, if the runner is a distance of ##\frac{1}{k}## from any other runner. Prove that each runner will be lonely at some point in time.

The Attempt at a Solution



So I obviously need to use induction for this. The case for ##k=1## is trivial, because there are no other runners, so that runner will always be a distance of ##\frac{1}{k}## from other runners. However, I'm stuck at this point, and am having trouble for cases where ##k\geq2##.
 
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AnTiFreeze3 said:

Homework Statement


Alright, so I have this problem from a textbook I'm using:

There is a track (of unit length) with ##k## runners on it. At the time ##t=0##, the runners start from the same position and take off simultaneously. Each runner has a distinct speed. A runner is said to be "lonely," at a time ##t##, if the runner is a distance of ##\frac{1}{k}## from any other runner. Prove that each runner will be lonely at some point in time.


The Attempt at a Solution



So I obviously need to use induction for this. The case for ##k=1## is trivial, because there are no other runners, so that runner will always be a distance of ##\frac{1}{k}## from other runners. However, I'm stuck at this point, and am having trouble for cases where ##k\geq2##.

What kind of calculus course is this? k=1 is trivial and you should certainly be able to handle k=2. Beyond that it gets really hairy. http://en.wikipedia.org/wiki/Lonely_runner_conjecture Looks to me like it's actually an unsolved problem.
 
Dick said:
What kind of calculus course is this? k=1 is trivial and you should certainly be able to handle k=2. Beyond that it gets really hairy. http://en.wikipedia.org/wiki/Lonely_runner_conjecture Looks to me like it's actually an unsolved problem.

Oh... wow :smile: That would explain my difficulty with the problem. Thanks for figuring that out!
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...

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