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I need help with a math problem

post #1 of 8
6/27/12 at 12:37pm
Thread Starter 
Hey guys!

I have an integral that I am not able to solve: http://i46.tinypic.com/c7uye.png

Can anyone help me with this beauty?

Thanks!
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post #2 of 8
6/27/12 at 4:13pm
Mathematica says thus:
http://integrals.wolfram.com/index.jsp?expr=%28x%281-x%29%29^%281%2F2%29&random=false

how to get there, who knows. Plus, the pi in front makes it seem as if it were some type of trigonometric function. (did you write the expression correctly? 1/4 then squared becomes square root)

cacio
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post #3 of 8
6/27/12 at 4:58pm
Is this part of a thesis?
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post #4 of 8
6/27/12 at 8:57pm
Thread Starter 
@cacio

You have to calculate a volume, so I wrote directly the whole integral. The formula is pi * integral a->b f^2(x) dx and in this case f(x)=x(x-1) under the radical and that 4 at the radical.

@dollars&scents

No, it is an exercise for entering at university
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post #5 of 8
6/27/12 at 8:58pm
Did you try Wolfram data app?
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post #6 of 8
6/28/12 at 3:41am
Thread Starter 
Yes, I did, but at some integrals you get in trouble. Let's take for example integral 1/1+x^4. There will be a mess when you can put it, in a more simple way, like this: 1/1+x^2^2 which is tan^-1x^2 + c.
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post #7 of 8
6/29/12 at 2:55pm
I just saw your tinyurl in the original posting. Perform the following substitution:

x = (1/2) * (t + 1)

This leads to the following trivial integral:

(PI / 4) * INT [-1 --> +1] dt { sqrt(1 - t^2) }

Since the integrand is just the equation for the upper half of a unit circle, the entire solution is then

(PI / 4) * (PI / 2) = (PI^2) / 8
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post #8 of 8
6/30/12 at 12:35am
6



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