Liber Abaci

Liber Abaci (1202) is an historic book on arithmetic by Leonardo of Pisa, known later by his nickname Fibonacci. Its title means The Book of Calculation. In this work, Fibonacci introduced to Europe the ten numerals (0, and 1 to 9) and the place-value system he had learned while travelling with Arabs in North Africa. Although the numerals were Indian in origin, they later became known as Arabic numerals because of Fibonacci's work. Before this, numbers in Europe were usually written using Roman numerals.

Liber Abaci was not the first Western book to describe Indian-Arabic numerals, but by addressing tradesmen rather than academics it was the book that convinced the public of the superiority of the new system. The first section introduces the Indian-Arabic number system. The second section presents examples from commerce, such as conversions of currency and measurements, and calculations of profit and interest. The third section discusses a number of mathematical problems. One example, describing the growth of a population of rabbits, was the origin of the Fibonacci sequence for which the author is most famous today. The fourth section derives approximations, both numerical and geometrical, of irrational numbers such as square roots. The book also includes Euclidean geometric proofs and a study of simultaneous linear equations.