Euclid's Muse

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Search Results for “ellipse”

By Phil Todd
Ellipse Incenter Locus
What is the locus of the incenter of the triangle formed by the string in the "two pins and a piece of string" construction of an ellipse?

Tags: ellipse, locus

By Phil Todd
Ellipse as locus of circle center
Take two overlapping circles.  Examine the locus of the center of the circles tangential to both. It seems to be an ellipse with foci at the centers of the two circles. Prove it.

Tags: ellipse, conic, focus

By Phil Todd
Polar Point Ellipse
The polar point of a line in an ellipse is a common point to the chords defined by the common tangents through the points on the line. Play with it and the meaning will be clear! (Go to Full Screen if the green points won't drag)

Tags: ellipse, polar

By Phil Todd
Ellipse Parametrization
We examine a standard parametrization of an ellipse.

Tags: ellipse, conic-section, parametrization

By Duncan
Focal Triangle
Create a triangle which has 3 points on the circumference of an ellipse, and two sides passing through the foci.  Look at 2 curves formed by the third side: the locus of its center and its envelope.  One is an ellipse, the other is not.

Tags: ellipse, focus

By Phil Todd
Projectile High Point
Press the play button to fire a projectile in the direction of the arrow. Move the arrow and try again. Notice the high points of the trajectory lie on an ellipse.  If the initial velocity of the projectile is v, and gravity is g, what is the equation of the ellipse?

Tags: projectile, parabola, ellipse, physics

By Phil Todd
Polar Line
The locus of the intersections of the tangents at the end of chords of an ellipse which pass through a common point is a straight line. A bit of a mouthful, but play with the diagram and it will become clear.

Tags: locus, polar, ellipse, conic

By Phil Todd
proof without words
A proof that the locus of the center of a circle tangential to two nested circles is an ellipse.

Tags: ellipse, focus

By Phil Todd
Trammel foci
Altering |AB| and |AC| changes the ellipse. Can you find a relationship between |AB|, AC| and |DE|, the distance between the foci?

Tags: ellipse, foci, trammel, principal-axes

By Phil Todd
Inverted Trammel
Archimedes trammel draws an ellipse if you fix the base and move the handle. What happens if you fix the handle and move the base? Drag point D to find out. See the curve.

Tags: trammel, ellipse

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