# Zu Chongzhi’s birthday

Zu Chongzhi (429-501) is one of the greatest ancient Chinese mathematicians. He was taught Mathematics from Liu Hui’s commentary on the *Nine Chapters on the Mathematical Art*. He was appointed as an officer in the city of Yang-chou and during this time he worked in Arithmetic and Geometry. He gave the rational 355/113 as an approximation of pi in his *Zhui shu* (“Method of interpolation”) and proved that:

3,1415926 < pi < 3,1415927

Zu also proposed a new calendar (the “Calendar of Great Brightness”) in 462 based on a cycle of 391 years with 144 extra months inserted (=4.836 months).

In the Wikimedia Commons there is this photo of a statue dedicated to him in Tinglin Park in Kunshan.

Google dedicated this doodle five years ago to celebrate his birthday.

**Location**: Tinglin Park in Kunshan (map)

# Pi Day’s doodle

Today is Pi Day!

Google published this doodle four years ago. We can see some formulas in it related with circles, spheres, trigonometry and the Archimedian value of pi.

# Pi is the guest star

One day by chance I discovered a Micajah Bienvenu’s sculptural work and I suppose that the picture that I had is due to the will of Destiny… I noticed that Pi was the great guest star of one of his sculptures! Reminding that discovery, I began to search in the net and I found that this Pi is or was installed at Harbor Steps in Seattle, near the corner of University St. and the 1st Avenue. However, I have not been able to discover whether the monument is still there or has been moved to another place because the author’s website says nothing about it.

**Localization**: map