Students learn to derive the formula for the area of a circle. They learn to relate a circle to a parallelogram and rectangle while learning the concept of infinity as they imagine slicing an circle into infinitesimally small slices.

This activity is a based on an activity I saw in Exploring Geometry with the Geometer's Sketchpad. Student will construct a trapeziod and then use rotation to create a parallelogram from the trapeziod. The follow up questions lead the...

How can trigonometry be used to find the area of a triangle or parallelogram? Does the triangle need to be a right triangle, and how accurate can the results possibly be? The answers to these questions are found here along with several...