Peter Weatherall: Circle Song
Peter Weatherall

Learn about the geometry of circles with Peter Weatherall’s Circle Song.

Mathalicious: Pizza Pi (HS)

In this lesson, students use the formula for the area of a circle to calculate how much of a pizza is actually pizza, and how much is crust.

Illuminations: Discovering the Area Formula for Circles
Illuminations (National Council of Teachers of Mathematics)

Using a circle that has been divided into congruent sectors, students will discover the area formula by using their knowledge of parallelograms.