September 28th, 2018, 09:00 AM  #1 
Member Joined: Sep 2014 From: Sweden Posts: 94 Thanks: 0  Find ellipse sector line length? So if I know a and b of the ellipse and also the angle of it. How can I calculate the curved line from the point of b to the point of a? I want the length of the curved line. For example: In a circle you can calculate the circle sector by knowing the angle and the radius.. If possible using a, b and the angle of the ellipse. How can you calculate the same thing for an ellipse? 
September 28th, 2018, 10:06 AM  #2 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1039  
September 28th, 2018, 01:15 PM  #3 
Member Joined: Sep 2014 From: Sweden Posts: 94 Thanks: 0 
So is it r1 + r2 = 2a that I should use to get the length of the curved line? I don't find the article clear about what gives me the curved lines length? 
October 17th, 2018, 02:14 PM  #4 
Newbie Joined: Oct 2018 From: Arizona Posts: 4 Thanks: 0 
There is no simple formula for arc length for an ellipse. The calculation leads to what are called Elliptic integrals, which are nonelementary. Google it and you will likely find more than you want to know.


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ellipse, find, length, line, sector 
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