Human: Who discovered the Riemann zeta function in complex analysis? Assistant: 
The Riemann zeta function is named after Bernhard Riemann, who first studied it in 1859. It is an important special function that is used in many areas of mathematics. It is also the most important example of a special function, which is a function that can only be expressed in terms of other special functions. The Riemann zeta function is a function that is defined as the sum of the series: