On November 11, 1675, German mathematician and polymath Gottfried Wilhelm Leibniz demonstrates integral calculus for the first time to find the area under the graph of y = ƒ(x).
On January 12, 1665, French lawyer and amateur mathematician Pierre de Fermat, famous for his research in number theory, analytical geometry and probability theory, passed away. He is best known for Fermat's Last Theorem, which he described in a note at the margin of a copy of Diophantus' Arithmetica.