We all learned that the ratio of the circumference of a circle to its diameter is called π and that the value of this algebraic symbol is roughly 3.14. What we weren't told, though, is that behind this seemingly mundane fact is a world of mystery, which has fascinated mathematicians from ancient times to the present. Mathematicians call it a "transcendental number" because its value cannot be calculated by any combination of addition, subtraction, multiplication, division, and square root extraction. This elusive nature has led intrepid investigators over the years to attempt ever-closer approximations. In 2002, a Japanese professor using a supercomputer calculated the value to 1.24 trillion decimal places! Nonetheless, in this huge string of decimals there is no periodic repetition. In this delightful layperson's introduction to one of math's most interesting phenomena, Drs. Posamentier and Lehmann review π 's history from prebiblical times to the 21st century, the many amusing and mind-boggling ways of estimating π over the centuries, quirky examples of obsessing about π (including an attempt to legislate its exact value), and useful applications of π in everyday life, including statistics. This enlightening and stimulating approach to mathematics will entertain lay readers while improving their mathematical literacy.

It is the ratio of the circumference of a circle to its diameter, a transcendental number, and to some people, an obsession. Posamentier (mathematics education, City College, CUNY) and Lehmann (mathematics, Humboldt U., Berlin) examine how pi has been an object of fascination from the Old Testament, through an act proposed in Indiana in 1897 setting its value, to a recent experiment with a supercomputer that netted a total of 1.24 trillion numbers to the right of the decimal point. Along the way they show how pi actually works according to Cusanus, Rumanujan, and even Wankel. The epilog contains pi expressed in 100,000 decimal places for the reader's enjoyment.
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In this delightful layperson's introduction to one of math's most interesting phenomena, the authors review pi's history from pre-biblical times to the 21st century.