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Trig function appears awkward to integrate

by Edmundb
Tags: appears, awkward, function, integrate, trig
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Edmundb
#1
Feb17-13, 07:07 AM
P: 2
I hope this isn't too simple for the maths forum.

I'm trying to find the length of the locus described by the bottom of a garage door as it is raised. It's all fairly straightforward until I have to integrate a function of the form

√ (sin2θ + k cos2θ)

k does not depend on θ. I tried several approaches to the problem and always came back to the above function.

In the end I integrated numerically and got my number which checks with reality. There's probably some nifty substitution but just I can't find it.
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JJacquelin
#2
Feb17-13, 07:32 AM
P: 759
See at the elliptic functions.
http://mathworld.wolfram.com/Ellipti...econdKind.html
Edmundb
#3
Feb17-13, 08:56 AM
P: 2
Thank you very much indeed. That looks like the clue I need. (As you've probably gathered I'm an Engineer and not a mathematician.)


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