Christoph Rudolff (born 1499 in

Jawor Jawor () is a town in south-western Poland with 22,890 inhabitants (2019). It is situated in the Lower Silesian Voivodeship. It is the seat of Jawor County, and lies approximately west of the regional capital Wrocław. One of the oldest towns ...

Silesia Silesia (see names #Etymology, below) is a historical region of Central Europe that lies mostly within Poland, with small parts in the Czech Silesia, Czech Republic and Germany. Its area is approximately , and the population is estimated at 8, ...

, died 1545 in

Vienna Vienna ( ; ; ) is the capital city, capital, List of largest cities in Austria, most populous city, and one of Federal states of Austria, nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. ...

) was a German mathematician, the author of the first German textbook on

algebra Algebra is a branch of mathematics that deals with abstract systems, known as algebraic structures, and the manipulation of expressions within those systems. It is a generalization of arithmetic that introduces variables and algebraic ope ...

. From 1517 to 1521, Rudolff was a student of

Henricus Grammateus Henricus Grammateus (also known as Henricus Scriptor, Heinrich Schreyber or Heinrich Schreiber; 1495 – 1525 or 1526) was a German mathematician. He was born in Erfurt. In 1507 he started to study at the University of Vienna, where he subsequen ...

(Schreyber from Erfurt) at the

University of Vienna The University of Vienna (, ) is a public university, public research university in Vienna, Austria. Founded by Rudolf IV, Duke of Austria, Duke Rudolph IV in 1365, it is the oldest university in the German-speaking world and among the largest ...

and was the author of a book computing, under the title: ' (Nimble and beautiful calculation via the artful rules of algebra

hich Ij () is a village in Golabar Rural District of the Central District in Ijrud County, Zanjan province, Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq ...

are so commonly called "coss"). He introduced the radical symbol (√) for the

square root In mathematics, a square root of a number is a number such that y^2 = x; in other words, a number whose ''square'' (the result of multiplying the number by itself, or y \cdot y) is . For example, 4 and −4 are square roots of 16 because 4 ...

. It is believed that this was because it resembled a lowercase "r" (for "radix"), though there is no direct evidence.

Florian Cajori Florian Cajori (February 28, 1859 – August 14 or 15, 1930) was a Swiss-American historian of mathematics. Biography Florian Cajori was born in Zillis, Switzerland, as the son of Georg Cajori and Catherine Camenisch. He attended schools firs ...

only says that a "dot is the embryo of our present symbol for the square root" though it is 'possible, perhaps probable' that Rudolff's later symbols are not dots but 'r's. Furthermore, he used the meaningful definition that ''x''⁰ = 1.

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''Die Coss Christoffs Rudolffs''
1499 births 1545 deaths Textbook writers People from Jawor 16th-century German mathematicians 16th-century German writers 16th-century German male writers {{Germany-mathematician-stub

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