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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

What I do in this question plz tell

MZk

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

First, for the 3rd time, get the formula for the surface area of the sphere.

**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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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

The surface area of a sphere is:

A=4pi r^{2}.

MZk

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

If surface area of sphere is 100pi cm^2 , it's radius will be

5

10

25

50

Since you know A = 100 pi you can substitute into that formula.

Do you know what to do now?

**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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**Mathegocart****Member**- Registered: 2012-04-29
- Posts: 1,880

Zeeshan, in the future, it would be preferable to try LaTeX or Codecogs so people can understand your statements.

The integral of hope is reality.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Well said, Latex is possible DK's greatest contribution to man.

**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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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

Haha I really know the formula but write 2 by mistake

Mathegocart hehe I think you people good in english so I wrote fast but you count every single statement

Next time I wrote complete question ok

MZk

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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

Ans is 5

MZk

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

r = 5 is correct.

**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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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

You know power series???

MZk

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Yes, I know lots of nice things about power series.

**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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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

Plz explain

MZk

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What would you like to have explained?

*Last edited by zetafunc (2017-01-22 03:46:08)*

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Plz explain

A power series can be thought of as a polynomial of infinite degree. The field is huge so you will have to narrow the questiion down. In computation, we use them often.

**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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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

Means???.

computation, we use them often.

MZk

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Polynomials are something we know a lot about. They are easy to compute, they have nice derivatives and integrals, we can find the roots numerically, they are faster for computers. Transcendental functions like e^x are another matter.

For instance if we have x^2 - 2x + 1 and x = 1 anybody who has some algebra can tell us the 1^2 - 2(1) + 1 = 0.

But if I ask what is e^x when x = 1? It is not so easy. To get that we use power series ( among other methods ).

**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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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

Hmm e^x at 1 is difficult to compute so which series used

MZk

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

The power series for e^x of course.

Notice that e^x has been replaced by powers of x.

**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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**iamaditya****Member**- From: Planet Mars
- Registered: 2016-11-15
- Posts: 694

Hi here are all the answers.

*Last edited by iamaditya (2017-02-06 23:31:17)*

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**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 648

Kk

MZk

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