## Fibonacci

Leonardo of Pisa, or Leonardo Fibonacci was born in Italy in 1175 AD. His greatest contribution to society was not, contrary to popular belief, the Fibonacci sequence (0, 1, 1, 2, 3, 5, 8, 13, 21...), but actually the introduction of the Hindu-Arabic number system, the system we use today. In his publication

It was in

*Liber Abaci*in 1202, he pointed out the practical advantages of the system, and began by introducing the ten "Indian figures", or digits 0-9. Using Roman Numerals was incredibly difficult for merchants, and they had to rely entirely on the abacus for calculations. Fibonacci exposed an alternate computing system, based in algorithms, such as adding and subtracting. He was the first to introduce the decimal point and positional calculations. Many of his techniques came from al-Khwarizmi, a Persian mathematician. Fibonacci demonstrated his mathematical skill in many more books, including*Liber Quadratorum*, addressing formulas and equations with perfect squares, and*Flos.*He also participated in math competitions in the court of Emperor Frederich II at Hohenstaufen.It was in

*Liber Abaci*that Fibonacci introduced the sequence. He introduced it through a problem addressing rabbit population, in which each successive year, the population increased to the next Fibonacci number. The sequence begins with 0 and 1 and each successive number is the sum of the two before it. This remarkable sequence is found in the petals and phyllotaxis of flowers and plants, tree and plant branching, population studies, and Golden Spirals-including the belt of Orion. The sequence is also a method of calculating the Golden Ratio; the Golden Ratio is based in Fibonacci. The ratio of once Fibonacci number to the one before approximates Phi more closely the farther you go in the sequence. By the 40th number, it approximates the Golden Ratio to the 15th digit.