How to Find the area of a circle using squares

In this video the instructor shows how to calculate the area of a circle using squares. She starts with the formula of the circumference which she says is circumference C = Pi * D, where D is the diameter of the circle. Now she says that you can turn the shape of circle into a square and compute the area of the square there by calculating the area of the original circle. She shows how to do this by cutting up the square into sectors and arranging them in the form of a rough square and calculating its area approximately. This video shows how to calculate the area of a circle by turning it into a square.