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Abu Kamil

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Abu Kamil Shujāʿ ibn Aslam ibn Muḥammad Ibn Shujāʿ was a major mathematician from Egypt. He lived during the Islamic Golden Age from approximately 850 to 930. He was often called Al-ḥāsib al-miṣrī, which means "The Egyptian Calculator." Abu Kamil was a master of both algebra and geometry. He was a successor to the mathematician al-Khwarizmi. Abu Kamil defended the work of al-Khwarizmi against others. He believed al-Khwarizmi was the true initiator and discoverer of algebraic principles.

Abu Kamil introduced several groundbreaking methods to the field of mathematics. He was the first mathematician to systematically use and accept irrational numbers as solutions. These are numbers that cannot be expressed as simple fractions. He also used these irrational numbers as coefficients in equations. He was the first Islamic mathematician to work easily with algebraic equations with powers higher than two. He could also solve sets of non-linear simultaneous equations that contained three unknown variables. Most of his work was written rhetorically. This means he wrote out math problems using words instead of symbols. For example, he used the Arabic expression "māl māl shayʾ" to represent $x^4$.

His most influential work was titled the Book of Algebra (Kitāb fī al-jabr wa al-muqābala). This book was written for advanced readers familiar with Euclid's Elements. Abu Kamil intended this work to expand upon the earlier algebra of al-Khwarizmi. The first chapter used geometry to teach algebra by solving problems with unknown variables and square roots. The second chapter addressed the six types of problems found in al-Khwarizmi's work. However, Abu Kamil worked out some of these problems directly without using geometrical proofs. The third chapter focused on quadratic irrationalities as solutions and coefficients. The fourth chapter showed how to use these irrationalities to solve problems involving polygons.

Abu Kamil's books covered many different mathematical topics. His Book of Rare Things in the Art of Calculation (Kitāb al-ṭarā’if fi’l-ḥisāb) focused on finding integral solutions for indeterminate equations. This is the earliest known Arabic work to seek solutions for this specific type of equation. He also wrote the Book of the Pentagon and Decagon (Kitāb al-mukhammas wa’al-mu‘ashshar). In this treatise, he used algebraic methods to solve geometric problems. He used the equation $x^2 + 10 = 10x$ to find a numerical approximation for the side of a regular pentagon. He also utilized the golden ratio in his calculations.

One of his most famous works was the Book of Birds (Kitāb al-ṭair). This small treatise taught how to solve indeterminate linear systems with positive integral solutions. The title comes from problems involving the purchase of different species of birds. Abu Kamil once discovered a problem that had 2,676 correct solutions. This discovery was so large that it caused great astonishment. Some people were even shocked or suspicious of his results. He wrote the book to make these complex calculations more accessible to others.

Abu Kamil also wrote practical manuals for everyday use. His book On Measurement and Geometry (Kitāb al-misāḥa wa al-handasa) was a manual for non-mathematicians. It was designed for people like land surveyors and government officials. The manual provided rules for calculating the volume and surface area of various solids. This included rectangular parallelepipeds, right circular prisms, square pyramids, and circular cones. He also provided rules for finding the area, diagonal, and perimeter of triangles, rectangles, and squares.

The legacy of Abu Kamil reached far beyond Egypt. His mathematical techniques were later adopted by the European mathematician Fibonacci. This helped introduce algebra to Europe through works like Fibonacci's Practica geometriae and Liber Abaci. Some of Abu Kamil's material was even incorporated into the Latin work Liber mahameleth by John of Seville. His works were translated into Latin by William of Luna in the 14th century. A Hebrew translation by Mordekhai Finzi appeared in the 15th century. His ability to enumerate all possible solutions to an equation remained unparalleled throughout the Middle Ages.

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