Represented in abbreviated form by the somewhat familiar sequence 3.14, pi, or the Greek letter π, is an iconic symbol seen in mathematical equations ... and the diameter of a circle.

This means that, using Pythagoras’ theorem, the equation of a circle with radius \(r\) and centre (0, 0) is given by the formula \(x^2+ y^2= r^2\). Find the equation of a circle with radius 3 ...

March 14 — a day you’re more likely than most others to eat — or throw — a pie and get a reduced price on your pizza. It’s ...