If we divide a circle into a number of equal segments then stack them in a row head-to-tail, the new shape is a parallelogram with bumpy sides, with the same area as the circle.
We can conclude the following:
1. The base of a parallelogram is approximately equal to half the circumference of the circle
2. The height of the parallelogram is approximately equal to the radius of the circle
3. The area of the parallelogram is equal to the area of the circle.