Paolo Dagomari da Prato (1282–1374), known in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

as Paulus Geometrus (''Paolo il Geometra'', "Paul the Geometer"), was a noted Florentine

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

and

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

, such a ''maestro dell'abbaco'' (master/teacher of the

abacus The abacus (''plural'' abaci or abacuses), also called a counting frame, is a calculating tool which has been used since ancient times. It was used in the ancient Near East, Europe, China, and Russia, centuries before the adoption of the Hi ...

) that he gained the epithet Paolo dell'Abbaco. Franco Sacchetti called him ''Paolo Arismetra e Astrologo'' (arithmetician and astronomer) and

Giorgio Vasari Giorgio Vasari (, also , ; 30 July 1511 – 27 June 1574) was an Italian Renaissance Master, who worked as a painter, architect, engineer, writer, and historian, who is best known for his work '' The Lives of the Most Excellent Painters, Sculp ...

''Paulo Strolago'' or ''Paolo Astrologo'' (astronomer). He reputedly had 6,000–10,000 pupils over the course of his life, being praised by contemporaries like Giovanni Gherardi da Prato, Filippo Villani, and

Giovanni Villani Giovanni Villani (; 1276 or 1280 – 1348)Bartlett (1992), 35. was an Italian banker, official, diplomat and chronicler from Florence who wrote the ''Nuova Cronica'' (''New Chronicles'') on the history of Florence. He was a leading statesman of ...

in his ''Cronica''. Paolo was born at Prato, the son of Piero Dagomari, who had moved to Florence. At Florence Paolo became the private tutor of

Jacopo Alighieri Jacopo Alighieri (1289–1348; sometimes written as Iacopo Alighieri) was an Italian poet, the son of Dante Alighieri, whom he followed in his exile. Jacopo's most famous work is his sixty-chapter ''Dottrinale''. He is represented by the father in ...

and a friend of Giovanni Boccaccio, who praised him highly in his '' De genealogia deorum gentilium''. The need for mathematics among the bankers and merchants of Florence led him to found a school of arithmetic ('' bottegha d'abacho'') at

Santa Trinita Santa Trinita (; Italian for "Holy Trinity") is a Roman Catholic church located in front of the piazza of the same name, traversed by Via de' Tornabuoni, in central Florence, region of Tuscany, Italy. It is the mother church of the Vallumbrosan ...

. In 1363 he held the priorate of the quarter of S. Spirito from May–June. Paolo died in Florence and was buried in Santa Trinita under a now-lost epitaph. His portrait, in fresco, is painted on the vault of the Galleria degli Uffizi. In mathematics Paolo introduced the

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

or comma as a device for separating numbers into groups of three for easing calculations on the order of thousands and millions. He is most famous for his work on equations (''aequationibus'') that fused

geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is ...

and arithmetic, which we today would recognise as

algebra Algebra () is one of the broad areas of mathematics. Roughly speaking, algebra is the study of mathematical symbols and the rules for manipulating these symbols in formulas; it is a unifying thread of almost all of mathematics. Elementary ...

. His most important mathematical treatise was the ''Regoluzze'', a manual of elementary arithmetic, written in 1340. Some of the "little rules" are:Robert Sabatino Lopez and Irving W. Raymond, ''Medieval Trade in the Mediterranean World'' (New York: Columbia University Press, 1951), p. 341 n2.

1. If you wish to write down number ofmany figures, make a period at every third figure beginning from the right hand and going towards the left, and then you will have as many thousands as are in front of the periods.
2. If you wish to multiply numbers ending with a zero, multiply their figures and put all of the zeros at the end.
15. If you wish to multiply fraction by fraction, multiply the numerators with one another, and the denominators similarly.
32. If you multiply the width of a circle by 22 and divide by 7, you will have the circumference.

Notes

{{DEFAULTSORT:Paolo Dagomari Di Prato 1282 births 1374 deaths 14th-century Italian poets Italian male poets 14th-century Italian mathematicians