Nl-.lt~.n,=n,nLO-~.]==[=~,nm R o b i n W i l s o n I

The Philamath's Alphabet-F F e r m a t : Pierre de Fermat (1601?-

1665) spent most of his life in Toulouse following a legal career. He considered mathematics a hobby, pub- lished little, and communicated with other mathematicians by letter. His two main areas of interest were ana- lytic geometry, analysing lines, planes and conics algebraically, and number theory, proving the 'little Fermat theo- rem' that for each positive integer a and prime p, a p - a is divisible by p. Fermat ' s ' last theorem' : In his copy of Diophantus's A r i t h m e t i c a , Fermat claimed to have 'a truly marvellous demonstration which this margin is too

narrow to contain' of the statement that for any integer n (> 2) there do not ex- ist non-zero numbers x, y and z for which x n + yn = z n. Fermat proved this for n = 4, using his 'method of infinite descent,' but it is highly unlikely that he had a general argument. Fermat's last theorem was eventually proved in 1995, after a long struggle, by Andrew Wiles. Fibonaeei: Leonardo of Pisa (c. 1170-1240), known as Fibonacci, is re- membered mainly for his L i b e r a b a c i

[book of calculation] which he used to popularise the Hindu-Arabic numerals, largely unknown in Europe, and pre- sent a wide range of mathematical puz- zles. The best known of these is on the breeding of rabbits and leads to the Fi- bonacci sequence 1, 1, 2, 3, 5, 8, 13 , . . . in which each successive term is the sum of the preceding two. Folium of Descartes: With his solu- tion of a problem of Pappus, Rend Descartes introduced algebraic meth-

ods into the solution of geometrical problems. He also discussed various curves, such as the 'folium of Descartes' with equation x 3 + y3 = 3axy.

Foucau l t ' s pendulum: In 1851 the French physicist Jean Foucault pre- sented his famous pendulum experi- ment, designed to demonstrate the ro- tation of the earth. A 28-kg ball was suspended from the roof of the Pan- thdon in Paris and allowed to swing. After a short time the swinging pendu- lum's path shifted, showing that the earth must be rotating. F rac ta l pa t t e rn : When a recurrence of the form Zn+ l = Zn 2 + C is applied to each point z0 in the complex plane, the boundary curve between those points that remain finite and those that 'go to infinity' is a fractal pattern, called a 'Ju- lia set' after the French mathematician Gaston Julia. This stamp shows a de- tall of the fractal pattern that arises when c = 0.2860 + 0.0115i.

Please send all submissions to the Stamp Corner Editor, Robin Wilson, Faculty of Mathematics, The Open University, Milton Keynes, MK7 6AA, England e-mail: r.j.wilson@open.ac.uk

7 6 THE MATHEMATICAL INTELLIGENCER �9 2004 Springer Science+Business Media, Inc.