FIBONACCI

Leonardo of Pisa, also known as Fibonacci, was a great mathematician during the middle ages.   He was born in Pisa, Italy, about 1175 AD.  He wrote the book entitled "Liber abaci", which was completed in 1202.  This book described the use of arithmetic in the decimal system.  Fibonacci discovered the sequence of numbers that later bears his name,  the Fibonacci series.  It has been shown that the Fibonacci series is closely related to the golden ratio, and can be observed in a variety of naturally occurring phenomena.