François Viète
The life of François Viète - Invented Algebra Under Banishment.
Vieta's Formulas
Relations between the coefficients of a polynomial and sums/products of its roots.
\[ \sum r_i = -\frac{a_{n-1}}{a_n}, \quad \prod r_i = (-1)^n \frac{a_0}{a_n} \]
Infinite Product for \(\pi\)
The first infinite product formula in mathematics.
\[ \frac{2}{\pi} = \frac{\sqrt{2}}{2} \cdot \frac{\sqrt{2+\sqrt{2}}}{2} \cdot \frac{\sqrt{2+\sqrt{2+\sqrt{2}}}}{2}
\dots \]
Sources: https://mathshistory.st-andrews.ac.uk/Biographies/Viete/
