Leonardo Fibonacci

  Leonardo Fibonacci was an Italian mathematician. Born Pisa, Italy, about 1170. Died about 1230.
Fibonacci was the outstanding mathematician of the Middle Ages. His famous work on arithmetic, alge­bra, and number theory, the Líber abad, carried on the work of Arable mathematicians and established Arabic numeráis and the decimal system throughout Europe. In this work, Fibonacci began the fruitful practice of representing various numbers in a problem by a single letter. He is known also for his discussion of an interesting sequence of numbers called the Fibonacci series.

Fibonacci spiral

Fibonacci numbers, also called the Fibonacci series, a series of numbers first studied by the Italian mathematician Leonardo Fibonacci (1170-1230). The series is usually written 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ... Each term in the series is the sum of the two preceding terms. Thus, the next term after 34 would be 55. The Fibonacci series is encountered in certain plants whose leaves spiral around their stems. In some of these plants, adjacent leaves may seem to have rotated through a half turn (½). However, in others the fraction may be 1/3, 2/5, 3/8, 5/13, 8/21, and so on. In these fractions both the numerators and the denominators form Fibonacci series.
   Fibonacci numbers are also connected with the golden section, a geometric ratio known to ancient philosophers. The golden section is created by dividing a line segment into two parts so that the ratio of the smaller part to the larger part is the same as the ratio of the larger part to the whole line segment.