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Reflections: mouthful of pi

Wee Kek Koon


Illustration: a yip


Having neither read Yann Martel's The Life of Pi nor seen Ang Lee's film adaptation, I fully intend to do both this year. Protagonist Piscine Molitor Patel calls himself "Pi" after the mathematical symbol "π", which represents the ratio of a circle's circumference to its diameter. Those of us who paid attention in school will know that pi is a number whose decimal fractions go on forever in a seemingly random sequence and is usually rounded off as 3.14.

In ancient China, the value of this ratio was taken approximately as three but, during the Eastern Han dynasty, the brilliant astronomer, mathematician, inventor, geographer, cartographer, poet and government official Zhang Heng (AD78-139) came up with the figure 3.1724. More than a century later, Wang Fan and Liu Hui, of the Three Kingdoms period (AD220-280), calculated it more accurately - as 3.156 and 3.1416, respectively. However, it was Zu Chongzhi (AD429-500), using rudimentary counting sticks, who pinned down pi with an accuracy that was unsurpassed globally for more than 800 years. Zu's approximation of pi correct to seven decimal places (between 3.1415926 and 3.1415927) was finally topped by Indian mathematician-astronomer Madhava of Sangamagrama (circa 1340-1425), who derived a value correct to 11 decimal places (3.14159265359).



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