 About Ellipses,
a selection of answers from the Dr. Math archives.
 Ellipse & Parabola Formulas  Dr. Math FAQ
 A conic (or conic section) is a plane curve that can be obtained by
intersecting a cone with a plane that does not go through the vertex of
the cone... If no line of the cone is parallel to the plane,
the intersection is a closed curve, called an ellipse.
 Uses of Ellipses
 Where are ellipses found in real life?
 Difference between Oval
and Ellipse
 What is the difference between an oval and an ellipse? Am I right
if I say that "all ellipses are ovals, but all ovals cannot be ellipses"?
 Perimeter of an Oval
 What is the perimeter of an oval called?
 Drawing an Ellipse
 Drawing An Ellipse
 How do you draw an ellipse with only a straight edge and a compass?
 Accurate Drawing of an Ellipse
 Draw an ellipse accurately using simple tools.
 Tracing an Ellipse
 How do you form an ellipse using 3 points?
 Area
 Ellipse Area and Circumference
 How can I draw an ellipse and find the area and circumference?
 Area of an Oval
 How do I figure out the area of an oval 17" x 38"?
 Area of an Ellipse using Integral Calculus
 How do you find the area of an ellipse?
 Area of an Ellipse without using Calculus
 How do you find the area of an oval without using calculus?
 Area of Part of an Ellipse
 Given an ellipse with a line bisecting it perpendicular to either the major
or minor axis of the ellipse, what is the formula for the area of the ellipse
either above or below that line?
 Area of an Ellipse Cut by a Chord
 How can you calculate area of the part of an ellipse cut off by a chord,
if you know the major and minor axes, and the chord?
 Area of A Sector of An Ellipse
 Finding the area of a sector of an ellipse, given the semiminor and major
axes and the angles of the 2 vectors bounding the sector.
 Perimeter
 Circumference of an Ellipse
 Is there a formula for determining the circumference or distance around
an ellipse?
 Formula for the Circumference of
an Ellipse
 What is the formula for the circumference of an ellipse?
 The Perimeter of an Ellipse or Oval
 What is the formula for calculating the perimeter of an oval, or an ellipse?
 Perimeter of an Ellipse
 Is there a formula that gives the exact perimeter of an ellipse?
 Equations, Graphing...
 Foci of an Ellipse
 If the major and minor axis of an ellipse are given, how do I find the
focus points?
 Graphing an Ellipse
 How do you graph an ellipse? What is the equation?
 Definition of an Ellipse
 The equation for an ellipse is Pf + Pr= 2a where P is a point on the ellipse
and f and r are the points of the foci. How do we know that this is true,
that Pf + Pr = 2a? How did we come up with the constant of 2a?
 Distance from Point to Ellipse
 How do you find the minimum distance from a point to an ellipse when
the point can be either inside or outside the ellipse?
 Ellipse Equation
 How do I get the equation of an ellipse, given four points and the
inclination of the major axis?
 Point on an Ellipse
 Given an ellipse and an arbitrary angle theta from either axis, how do
you find the coordinates of the intersection of the ellipse and a vector
formed by angle theta?
 Points within an Ellipse
 How to generate points that will be within an ellipse.
 Folding a Circle to Get an Ellipse
 How can I prove that taking a point on a circle, folding it to an interior
point, and repeating this process creates an envelope of folds that forms an
ellipse?
 Ellipse Geometry
 I wish to draw a line departing at a given angle from the long axis
of an ellipse and bisecting the perimeter of the ellipse at right angles
to the tangent at that point...
 Tangent Common to Two Ellipses
 I have two general ellipses in space and I want to find the equation
of the tangent common to these ellipses.
 Slope of Tangent to an Ellipse
 If I know a point on an ellipse, how do I find the angle of the
ellipse at that point?
 Finding the Axes of an Ellipse
from a Known Cone
 I'm trying to solve a specific situation regarding lighting when
viewed as an oblique circular cone...
