# A Trillion Pieces of Pi

The number pi (p) represents the ratio of a circle's circumference to its diameter. Starting with 3.1415926535897932384. . ., its digits run on forever. That hasn't stopped researchers from trying to calculate as many of those digits as computer technology and mathematical methods allow.

Computer scientist Yasumasa Kanada and his coworkers at the University of Tokyo Information Technology Center have now succeeded in computing 1,241,100,000,000 decimal digits of pi, smashing their own previous world record of 206,158,430,000 digits, set in 1999. The calculation required about 602 hours on a Hitachi SR8000 computer, with access to a memory of about 1 terabyte.

To calculate the digits of pi, Kanada and his team used formulas involving arctangent relations of pi. For instance, you can use the following expression to work out the value of the arctangent of *x* to any desired number of decimal places just by evaluating the series to a sufficiently