# Search Results for “ellipse”

##### 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?##### 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)

##### 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.##### 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.##### 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.##### proof without words

A proof that the locus of the center of a circle tangential to two nested circles is an ellipse.##### Trammel foci

Altering |AB| and |AC| changes the ellipse. Can you find a relationship between |AB|, AC| and |DE|, the distance between the foci?##### 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.##### Epic Circle Trace 3

Four points are located proportionally around a circle, according to four different functions of*t*. A figure connecting the four points is traced through

*t*. What are the four functions? Look at the .gx source for the answer.

**Tip**: press "go" to animate

*t*at a constant rate from 0 to ∏ and back, looped.