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Shahram Zafary

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Feb 6, 2009, 10:46:58 AM2/6/09
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Dear Sir;

I have found out a single term formula for approximating the circumference of ellipse and I hope to print, and publish it. This formula is very simple and accurate.
I will be grateful if you help and guide me about it.
Sincerely:

Shahram zafary
Semnan, Iran

curious george

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Feb 6, 2009, 10:58:50 AM2/6/09
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"Shahram Zafary" <shahram...@yahoo.com> wrote in message
news:1810883.12339352486...@nitrogen.mathforum.org...

post it here.


Noone

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Feb 6, 2009, 11:33:53 AM2/6/09
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If you have not already done so, I suggest you look at the material at
the following link to see if your formula improves upon previous work
on this subject.
<http://home.att.net/~numericana/answer/ellipse.htm#elliptic>

Math Helper

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Feb 6, 2009, 4:41:11 PM2/6/09
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How unusual! An imbecile posting from mathforum.org!

"Shahram Zafary" <shahram...@yahoo.com> wrote in message
news:1810883.12339352486...@nitrogen.mathforum.org...

> Dear Sir;
>
> I have found out a integral bigger than the equals sine! More
> impotent blithering has never been....


Michael Press

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Feb 8, 2009, 5:55:24 AM2/8/09
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In article
<1810883.12339352486...@nitrogen.mathforum.org>,
Shahram Zafary <shahram...@yahoo.com> wrote:

> Dear Sir;
>
> I have found out a single term formula for approximating the circumference of ellipse and I hope to print, and publish it. This formula is very simple and accurate.
> I will be grateful if you help and guide me about it.

Arithmetic-Geometric mean:

a_{n+1} = (a_n + b_n)/2
b_{n+1} = sqrt{a_n * b_n}
c_{n+1} = (a_n - b_n)/2
M(a, b) = lim_{n -> oo} a_n = \lim_{n -> oo} b_n

K(k) and E(k) are the complete elliptic integrals of the
first and second kind. k' = sqrt{1 - kk}.

K(k) = int_0^{pi/2} du / sqrt{1-k^2.sin^2 u}
= pi / (2.M(1, k'))

E(k) = int_0^{pi/2} sqrt{1-k^2.sin^2 u} du
= (1 - S) K(k)

where S = sum_n 2^{n-1}.(c_n)^2.

The perimeter, A, of an ellipse with semiaxes a and b,
0 < b <= a is given by

A = 4.a.E(k')
= (aa - S).2.pi/M(a, b)

where a_0 = a, b_0 = b, c_0 = aa - bb.

This will give the perimeter of the ellipse to 5 significant
figures with 4-6 iterations for e < .99, where e is the
eccentricity. The AGM converges quadratically so one more
iteration will give 10 significant figures.

So unless you know exactly how much accuracy you want at
compile time and are prepared to engineer approximations
for the full range of eccentricities that will be called
for, and absolutely need the speed of specialized
approximations, use the AGM as it will give answers with
accuracy specified at run time, and will not take much
time doing it.

Might as well code up the AGM and see how it performs anyway.

--
Michael Press

Shahram Zafary

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Apr 1, 2009, 9:18:03 AM4/1/09
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MY FORMULA IS MORE SIMPLE AND ACCURATE ONE FOR EVERY VALUE OF ECCENTRICITY(e).

Shahram Zafary

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Apr 1, 2009, 9:24:54 AM4/1/09
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THANK YOU FOR YOUR SUGGESTION BUT MY FORMULA IS MOST SIMPLE AND ACCURATE ONE FOR EVERY VALUE OF ECCENTRICITY(e).

David W. Cantrell

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Apr 1, 2009, 10:02:50 AM4/1/09
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Shahram Zafary <shahram...@yahoo.com> wrote:
> MY FORMULA IS MORE SIMPLE AND ACCURATE ONE FOR EVERY VALUE OF
> ECCENTRICITY(e).

As I suggested to you moments ago in geometry.pre-college, posting your new
formula in a newsgroup will establish that you discovered it. And posting
it would allow us to see how simple and accurate it is, etc.

David W. Cantrell

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