Pi began being symbolized by the pi symbol (π) in the 1706 by the British mathematician William Jones. Jones used 3.14159 as the calculation for pi. Pi r squared. In basic mathematics, pi is used to find area and circumference of a circle.Pi is used to find area by multiplying the radius squared times pi, or. So in trying to find the area of a circle with a radius of 3 centimeters, π3 2 = 28.27 cm.y definition, pi is the ratio of the circumference of a circle to its diameter. In other words, pi equals the circumference divided by the diameter (π = c/d). Conversely, the circumference is equal to pi times the diameter (c = πd).