Pi is the ratio of the circumference to the diameter of a circle, which is generally expressed by the Greek letter π.

π is also equal to the ratio of the square of the area and radius of a circle, which is the key value to accurately calculate the geometric shapes such as the circumference of a circle, the area of a circle and the volume of a ball. In the analysis, π can be strictly defined as the smallest positive real number x satisfying sinx=0.

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π is the lowercase of the sixteenth Greek letter. The symbol π is also the first letter of Greek π ε ρ ρ ρ α (meaning periphery, region, circumference, etc. ).

1706, the British mathematician William Jones (1675- 1749) first expressed pi. 1736, the great Swiss mathematician Euler also began to express pi. Since then, π has become synonymous with pi.

Be careful not to mix π with its capital π, which means multiplication.