Area of an Ellipse

What is the area of an ellipse with equation ?
This ellipse is the image of the unit circle under the transformation , .
This transformation maps a square into a rectangle whose area is times the area of the square.
Unions of disjoint squares inside (or crossing) the circle are mapped into unions of disjoint rectangles inside (or crossing) the ellipse.
The area of the ellipse must therefore be times the area of the unit circle, or .
The Demonstration maps squares with side into rectangles with sides and and computes inner and outer approximations to the areas of the unit circle and the image ellipse.
The difference between the outer and inner areas for the circle is less than , where , and hence the difference between the outer and inner areas for the ellipse is less than .


  • [Snapshot]
  • [Snapshot]
  • [Snapshot]


R. B. Kirchner, "The Area of the Ellipse," The American Mathematical Monthly, 68(7), 1961 p. 653.
    • Share:

Embed Interactive Demonstration New!

Just copy and paste this snippet of JavaScript code into your website or blog to put the live Demonstration on your site. More details »

Files require Wolfram CDF Player or Mathematica.