Archimedes used it to calculate the area of a circle with a different formulation than Euclid's assertion that it is proportional to r².

Finding the area of a circle is easy with pizza and infinity. One of the oldest calculus problems, finding the area of a circle, can be visualized using a pizza. By dividing it up into ever ...

The mathematical constant, which is the ratio of a circle’s circumference to its diameter, can be used to find the area or circumference of a circle -- or of that pie you’re hopefully enjoying ...