The vertical side of this rectangle is the radius of the circle and the length of the side is half of the circumference (so, 2π R). Yes, the area of this rectangle would be π R2.

The radius is always half the length of the diameter. If you know the radius of this circle is 6cm, can you work out the diameter?

One of the oldest calculus problems, finding the area of a circle, can be visualized using a pizza. By dividing it up into ever smaller slices and laying them out next to one another, eventually ...