**PORTRAITS FROM THE PAST**

**Al-Khwarizmi**

When people measure their weight or tally the cost of their groceries, many use Hindu-Arabic numerals. Why “Hindu-Arabic”? The basis of the modern number system that uses the digits zero to nine appears to have developed in India and to have made it to the West by way of medieval scholars who wrote in Arabic. Foremost among them was a man named Muhammad ibn-Musa al-Khwarizmi. Likely born in what is now Uzbekistan in about 780 C.E., al-Khwarizmi is called the “great hero of Arabic mathematics.” Why did he receive this acclaim?

**“HERO OF ARABIC MATHEMATICS”**

Al-Khwarizmi wrote about the practical use of decimals and also clarified and popularized a method for solving certain mathematical problems. He explained the method in his work *The Book of Restoring and Balancing.* The term *al-jabr* in its Arabic title, *Kitab al-jabr wa’l-muqabala,* is the source of the English word algebra. Algebra, says science writer Ehsan Masood, is considered “the single most important mathematical tool ever devised, and one that underpins every facet of science.”*

“Countless generations of high school students wish [al-Khwarizmi] hadn’t bothered,” quips one author. Be that as it may, al-Khwarizmi stated that his aim was to explain methods in order to simplify calculations in trade, the division of inheritances, surveying, and so on.

Centuries later, Western mathematicians, including Galileo and Fibonacci, held al-Khwarizmi in high esteem because of his clear explanations regarding the use of equations. Al-Khwarizmi’s descriptions paved the way for further studies in algebra, arithmetic, and trigonometry. The latter enabled Middle Eastern scholars to calculate values for angles and sides of triangles and to advance studies in astronomy.*

Algebra: “The single most important mathematical tool ever devised”

Those who built on al-Khwarizmi’s work developed new ways to use decimal fractions and pioneered new techniques to determine area and volume. Middle Eastern architects and builders used such advanced methods long before their Western counterparts, who became familiar with them during the Crusades. They later took the knowledge home, aided by educated Muslim captives and immigrants.

**ARABIC MATH SPREADS**

In time, al-Khwarizmi’s works were translated into Latin. The Italian mathematician Fibonacci (c. 1170-1250), also known as Leonardo of Pisa, is generally credited with popularizing Hindu-Arabic numerals in the West. He learned about them during his travels in the Mediterranean world and thereafter wrote his *Book of Calculation.*

Al-Khwarizmi’s explanations took centuries to become well-known. But now his methods and the mathematics related to them are the very lifeblood of science and technology, not to mention commerce and industry.

In modern algebra, unknown numbers are represented by letters, such as *x* or *y*. An example is the equation *x* + 4 = 6. Subtracting 4 from both sides of the equation reveals that *x* equals 2.

Greek astronomers pioneered the work of calculating the sides and angles of triangles. Islamic scholars used trigonometry to determine the direction to Mecca. Muslims like to pray facing Mecca. Tradition requires that the dead be buried facing Mecca and that Muslim butchers face Mecca when killing animals for meat.