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#1 2014-06-29 01:59:40

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,789
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Area by Integration

I've three functions: f(x), g(x) and h(x). How do I find the area they enclose?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#2 2014-06-29 02:38:21

ElainaVW
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Registered: 2013-04-29
Posts: 306

Re: Area by Integration

Hello:

I guess that a question phrased like that would get many down votes at the SE.

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#3 2014-06-29 03:16:24

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,789
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Re: Area by Integration

But this is not SE! smile


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#4 2014-06-29 04:15:39

bob bundy
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Registered: 2010-06-20
Posts: 6,528

Re: Area by Integration

Sketch them (good practice for any integration anyway).  Then find where they intersect.  Then adopt a strategy for getting the area you want.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#5 2014-06-29 04:42:52

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,789
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Re: Area by Integration

So, there is no magical formula?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#6 2014-06-29 17:57:40

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,455

Re: Area by Integration

Is the simplest idea for between two functions provided f(x) is the function on top.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#7 2014-06-29 19:15:50

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,528

Re: Area by Integration

hi Agnishom,

These three functions may show you the difficulty coming up with a single formula.

huRmbuo.gif

1 is sin(x)
2 is 2sin(x)
3 is (x-1.5)^2

The enclosed area would be

difference between 2 and 3 in the region a to b
difference between 2 and 1 in the region b to c
difference between 2 and 3 in the region c to d.

Until you know those crossing points you cannot decide the values of a, b, c and d.

And a small change in one function would change everything.

Bob

Last edited by bob bundy (2014-06-29 19:19:07)


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#8 2014-07-10 23:27:29

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,789
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Re: Area by Integration

Okay. So what should have been my question?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#9 2014-07-10 23:28:54

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,455

Re: Area by Integration

Post a problem.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#10 2014-07-10 23:37:02

Agnishom
Real Member
From: The Complex Plane
Registered: 2011-01-29
Posts: 18,789
Website

Re: Area by Integration

I do not have any


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#11 2014-07-10 23:39:12

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,455

Re: Area by Integration

What inspired the original question?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#12 2014-07-11 01:05:59

Agnishom
Real Member
From: The Complex Plane
Registered: 2011-01-29
Posts: 18,789
Website

Re: Area by Integration

The rhombus area problem


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#13 2014-07-11 01:12:25

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,455

Re: Area by Integration

I am sorry, I do not remember it.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#14 2014-09-02 09:23:14

αβγ
Member
Registered: 2014-09-02
Posts: 19

Re: Area by Integration

You can't really use a magical formula to obtain the answer easy peasy because you have 3 functions, each with their own graph.  Since I don't know how the graphs are oriented and how they intersect, the only actual answer without anymore information would be the sum of the negative or positive of each integral of each function, i.e.:

That's the most precise answer (in reduced form) that can be obtained without further information.


α as in alpha stands for "a love of math"
β as in beta stands for "being skilled in the latter"
γ as in gamma stands for "getting sick of homework"

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