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#1 2014-11-19 20:21:29
- Saman Q
- Guest
Solving Integral problem.
I'm sure you guys are familiar with finding the surface area with the help of integrals ! (sorry for my bad English) so i could solve the problems with two functions but i confronted this problem that has 3 functions :
Calculate the surface area between these functions with the help of integrals :
Y=1/x^2 , Y=x , Y=1/8x
I could calculate the surface with drawing its diagrams but i don't know how to use integrals directly ! I am at my first semester at university studying Mathematics In Iran just for you guys to know my level so i will appreciate any help from you guys 
#2 2014-11-19 20:34:34
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Solving Integral problem.
Hi;
Is that
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#3 2014-11-19 22:13:32
- Saman Q
- Member
- Registered: 2014-11-19
- Posts: 4
Re: Solving Integral problem.
Sorry i meant Y=X/8
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#4 2014-11-20 14:11:32
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Solving Integral problem.
Hi;
Did you graph the equations? Did you get the points of intersection A,B and C?
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#5 2014-11-20 18:41:21
- Saman Q
- Member
- Registered: 2014-11-19
- Posts: 4
Re: Solving Integral problem.
Yes i did B is (1,1) , C is (2,1/4) and A is (0,0) then i found the surface with the help of shapes not the integrals ! do you know how to find it only with the help of integrals !
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#6 2014-11-20 20:37:14
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Solving Integral problem.
Hi;
The points of intersection are found by algebra. You find the area with integrals.
Do you agree that the area you need to find is the area in red?
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#7 2014-11-20 21:15:40
- Saman Q
- Member
- Registered: 2014-11-19
- Posts: 4
Re: Solving Integral problem.
Yes i agree.
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#8 2014-11-20 22:27:53
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Solving Integral problem.
Then the problem can be broken down into two pieces. The first piece looks like this:
That area is found by
Do you see why and can you do the integrations?
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#9 2014-11-21 00:32:39
- Saman Q
- Member
- Registered: 2014-11-19
- Posts: 4
Re: Solving Integral problem.
Thanks i got it 
so the second part is ∫1/(x²) dx _∫x/8 dx from 1 to 2 then we add the two parts ! THANK YOU VERY MUCH
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#10 2014-11-21 02:17:35
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Solving Integral problem.
Hi;
Hope that helped and welcome to the forum.
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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