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Well, I'm sorry to bother you all with this exercise, but I can't seem to find the solution.

First of all: no, this is NOT a homework, it's just an exercise in our book, and I'm curious as to what the solution is. I've been trying to find it for over an hour straight, and I just can't figure it out.

A man starts to walk in point P and walks around a circular lake (radius: 3.2 km) with a constant speed of 4.8 km/hour. The position of the man is R.
How fast does the length of the cord PR change, when PÔR = 60°?

Oh, and we saw this exercise with Derivatives, just mentioning ;-)
Anyone care to try?

Or you could tell us where Ô is. The angle PÔR is meaningless if you don't define Ô. If Ô is the centre of the lake the length of the cord PR changes at 4.8*sin60=4.157km/hour when PÔR = 60°

Last edited by Andrew Benton; 11-11-2004 at 09:09 AM.

Explaining the answer would either involve a bunch of formulas (if you want calculus and derivatives used in the explanation) or a bunch of drawings (if you want an explanation using vector analysis), both of which are most easily provided by sitting at a desk with you.

Maybe you can make our lives a little easier by explaining what you are trying to do and how far you've got?

Well, I'm trying to calculate it using calculus and derivatives.
I'm sorry for bothering you all with this, and I feel rather stupid asking this question (normally, I don't have any problems calculating derivatives).

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