The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Math Topics » geometry.pre-college

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: A single term formula for calculating the circumference of ellipse
Replies: 8   Last Post: Jan 6, 2013 3:37 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
David W. Cantrell

Posts: 3,395
Registered: 12/3/04
Re: A single term formula for calculating the circumference of ellipse
Posted: Jun 14, 2009 1:31 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Shahram Zafary <> wrote:
> Hello dear Mr. Cantrell.
> Thanks a lot, for your really exact comments on my formula.
> I am really grateful and hope you permit me contact you again about this
> formula and some same findings that I found out before

Dear Mr. Zafary,

You are certainly welcome to contact me using my email address.

I mentioned your nice formula to Gerard Michon recently, and he has now
added a section about it on his Numericana site. See


Note that Gerard found a very nice alternative way of writing your
approximation: The quantity h = ((a - b)/(a + b))^2 often appears in
dealing with the perimeter of an ellipse. Using h, your approximation can
be written simply as

pi (a + b) (4/pi)^h

Although I really liked your approximation before, I like it even more in
the form above!

Best regards,

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.