MathGroup Archive 1999

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circumference of an ellipse

  • To: mathgroup at
  • Subject: [mg19299] circumference of an ellipse
  • From: "M.J.M. Maes" <mar.maes at>
  • Date: Thu, 12 Aug 1999 22:34:51 -0400
  • Organization: Planet Internet
  • Sender: owner-wri-mathgroup at

I made a little spreadsheetfile to calculate the circumference (length) of
an ellipse using an iterative process.
When I compare the results with the results of a formula to approximate the
 - which is pi(3(a+b)-sqrt((a+3b)(3a+b))) - the difference is greater then I
expected (a few percents).
This may be a shortcoming of the approximation formula, or of my
Could someone please give me the exact results (in 10 or 15 digits) of some
a=2; b=1
a=5; b=1
a=100; b=26

Thanks in advance!


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