The first systematic efforts to find a numerical approximation for $\pi$ was made by Archimedes (240 B.C.), who proved that $\frac{22}{7}$ < $\pi$ < $\frac{223}{71}$ by finding the perimeter of the polygons inscribed in and circumscribed about a circle.

In about A.D. 480 the Chinese physicist Tsu Ch'ung-chih gave the approximation, Which is correct to six decimals.

$\pi$ = $\frac{355}{113}$ = $3.141592....$

This remained the most accurate estimation of $\pi$ until the Dutch mathematician Adrianus Romanus (1593) used polygons with more than a billion sides to compute $\pi$ correct to 15 decimals. The Englishman William Shanks spent 15 years (1858-1873) using infinite serious and trigonometric identical methods to compute $\pi$ corrected to 707 decimals. And later it was found that this figures were wrong beginning with the 528th decimal. Today with help of computers one can calculate $\pi$ value corrected to millions of decimal.

The value of pi find more application in algebra. The following are examples which make use pi value for the calculation.

**1. Formula for the area (A) of a circle also uses $\pi$**

A = $\pi r^{2}$

**2. Formula for the volume of sphere**

Volume (V) =

$\frac{4}{3}$ $\pi r^{3}$

**3. Perimeter of a circle** = $2 \pi r$