Explore Geometry


How Eratosthenes Calculated the Circumference of the Earth

While Eratosthenes was not the first to estimate the circumference of the earth, his was the most accurate of the ancient estimates. Here is how he did it.

Perpendicular Bisector of a Chord

A chord is a line segment with end points on a circle. When we construct a perpendicular bisector of a chord, we create a figure with interesting properties.

Geometry and Numbers

In ancient Greece nearly all math had roots in geometry. They even did multiplication geometrically.

The Kite

The kite is a figure with many interesting properties. Begin exploring the kite here.

Properties of Right Triangles Incribed in Circles

There are several interesting relationships between right triangles and their circumscribing circle.

Drawing an ellipse given two circles with the same center.

An ellipse can be outlined using two circles with the same center.

Constructing an Ellipse Given a Circle and Inscribed Rectangle.

An ellipse can be outlined using a circle and a rectangle inscribed in the circle.

Geometric Nets

A 'net' is a two dimensional (flat) figure that can be folded into a three dimensional geometric shape. You can use these nets to build your own geometric shapes. For best results, print these on card stock.