Liu Hui, a great mathematician of the state of Cao Wei, provided a detailed commentary on the Nine Chapters on the Mathematical Art.
Using an inscribed polygon, he successfully calculated the area with a 96-sided polygon to demonstrate that Pi is approximately 3.14 or 157/50.
He noted that the larger the number of sides, the closer the area becomes to the circle, leaving no area left out.
Zu Chongzhi extended Liu Hui's method. He proved mathematically that Pi lies strictly between 3.1415926 and 3.1415927.
He provided two rational approximations for Pi: