I need to explain how to derive the formula for the area of a circle from the formula for the area of a rectangle. The area of a rectangle is length(width) and the formula for the area of a circle is $\pi r^2$
My original idea was to partition the circle into an even number of sections, say 6, and then cut one of the sections in half so we would have 7 sections. When you lay out the sections you will have a rectangle- but I can't seem to get the formula of a circle from that... any advice??