Pi << py >> is the ratio of the circumference (C) of a circle to its diameter (d). The ratio is the same constant for every circle and is approximately 3.14159. It is represented by the Greek letter π (pi). Hence, C = π d.
Pi is used in many mathematical calculations. For example, pi is used to calculate the areas of circles and the volumes of spheres and cones. The area (A) of a circle with radius r is given by the formula A = πr2. The volume (V) of a sphere with radius r is given by the formula V = 4/3 π r3. The volume of a circular cone with radius r and height h is given by the formula V = 1/3 πr2h. Many formulas that describe such phenomena as the motion of a pendulum or the vibration of a string use pi as well.
Pi is an irrational number. An irrational number cannot be written as a ratio of integers. Mathematicians have developed clever algorithms (procedures) that, when combined with computer calculations, have yielded tens of trillions of decimal digits of pi.
