for square roots (the first to use
this notation) and 
for
cube roots and 
for 4 th
roots. He has the idea that x0 = 1 which is important.
Christoff Rudolff studied algebra at the University of Vienna, between 1517 and 1521. He reed in Vienna after studying at the university and earned his living giving private lessons in mathematics. He did use the facilities offered by the university, being able to use books in the university library and talking with academics at the university.
Rudolff's book Coss, written in 1525, is the first
German algebra book. The reason for the title is that cosa is a thing
which was used for the unknown. Algebraists were called cossists, and
algebra the cossic art, for many years. Rudolff calculated with
polynomials with rational and irrational coefficients and
was aware that ax2 + b = cx has 2 roots. He used
for square roots (the first to use
this notation) and for
cube roots and for 4 th
roots. He has the idea that x0 = 1 which is important.
The year after Coss appeared Rudolff produced Künstliche Rechnung mit der Ziffer und mit den Zahlpfennigen. This studied applications of mathematics to commerce.