Christoff Rudolff (born 1499 in Jawor, Silesia, died 1545 in
Vienna) was the author of the first German textbook on algebra.
Rudolff was from 1517 to 1521 a student of Henricus Grammateus
(Schreyber from Erfurt) at the University of Vienna and was the
author of a book computing, under the title: Behend und hübsch
Rechnung durch die kunstreichen regeln Algebre. He introduced
the radical symbol (√) for the square root. It is believed that
this was because it resembled a lowercase "r" (for "radix"),
though there is no direct evidence. Cajori 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 x0 = 1. - ^ a b Walter William Rouse Ball
(1960), A short account of the history of mathematics (4 ed.),
Courier Dover Publications, p. 215, ISBN 978-0-486-20630-1 - ^ a
b Howard Whitley Eves (1983), Great moments in mathematics
(before 1650: Volume 1),