<human>:  I have a question about the history of mathematical analysis. What is the first mathematical proof that was published in the 20th century?
<bot>: The first mathematical proof published in the 20th century was the proof of the Riemann hypothesis by Hermann Weyl in 1904. The Riemann hypothesis is a conjecture in number theory that states that all non-trivial zeros of the Riemann zeta function lie on the critical line.