This slideshow lesson is fully interactive and goes with the AREA OF A CIRCLE WS and is free so you can see my work! I have over 175 ppts available on http://www.mathslideshows.com/
The lesson starts by having students cut out a circle and label the circumference, diameter and radius. Next the students cut the circle on the diameter so that they have 2 semi circles. Next the students cut the radius of each semicircle but not to the outside edge. Then they fold the cut triangles to look similar to 4 teeth. They do this to both pieces. Then they fit both sets of teeth (or slices of pie) together to form a parallelogram. Next the students tape this figure to their AREA OF A CIRCLE WS (the free one.)
The slideshow lesson continues by having students label certain parts of their taped figure and answer questions to eventually discover the area of a circle is pie times radius squared.
THE ANIMATION ON THIS IS GREAT! I love this demonstration because it shows how something works so students understand the formula.
The lesson continues with several examples for students to try. The lesson ends with study guide notes for students to take at the end, which review all concepts taught in the lesson.
To see more information on the all of the math slideshows visit