1. Persian mathematician, Mohammed ibn-Musa al-Khwarizmi, suggested that a little circle should be used in calculations if no number appeared in the tens place. Arabs called this circle "sifr," or "empty." Zero was crucial to al-Khwarizmi, who used it to invent algebra.
2. Al-Khwarizmi also developed quick methods for multiplying and dividing numbers, which are known as “algorithms” — a corruption of his name.
Zero found its way to Europe through the Moorish conquest of Spain and was further developed by Italian mathematician Fibonacci.
3. Al-Khwarizmi's treatise on algebra (Compendious Book on Calculation by Completion & Balancing, c. 813 CE) presented the first systematic solution of linear and quadratic equations. The term algebra comes from the title of his book, al-jabr meaning "completion" or "rejoining".
4. Al-Khwarizmi is usually credited with the development of lattice (or sieve) multiplication method of multiplying large numbers, a method algorithmically equivalent to long multiplication. His lattice method was later introduced into Europe by Fibonacci.
5. In addition to inventing algebra, Al-Khwarizmi developed the first quadrant (an instrument used to determine time by observations of the Sun or stars), and revised Ptolemy's “Geography”, consisting of a list of 2,402 coordinates of cities throughout the known world.
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