Logarithm
Logarithms were first used in India in the 2nd century BCE. The first to use logarithms in modern times was the German mathematician Michael Stifel (around 14871567). In 1544, he wrote down the following equations:  and . This is the basis for understanding logarithms. For Stifel,  and  had to be whole numbers. John Napier (1550–1617) did not want this restriction, and wanted a range for the exponents.