Measuring the circumference of an ellipse ```Name: existing Status: N/A Age: N/A Location: N/A Country: N/A Date: Around 1995 ``` Question: Is there any way to evaluate the circumference of an ellipse (when it is not a circle) exactly? Replies: Approximately: 2 * pi * sqrt[(a^2 + b^2)/2] Exactly: 4 * a * E where E is an elliptic integral with k = sqrt[a^2 - b^2]/a hawley Revised April, 2001 I remember one from Ramanujan, and suggest the following addendum... see: http://forum.swarthmore.edu/dr.math/faq/formulas/faq.ellipse.circumference.html for the following approximation due to Ramanujan: C ~~ (3a + 3b - sqrt[(a+3b)(b+3a)]) additionally, about _vinculum_ I seem to remember the more usual word for chain in Latin is _catena_ from which we get "catenary" (the hanging chain curve) and "concatenate" (joining with a chain, or joining the links of the chain together).... Gratiae!!! (thanx) for the Latin lesson in a most unexpected place! Bob "A" Click here to return to the Mathematics Archives

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