# Bernoulli, Jakob** or **Jacques[ber**noo**lee](1655--1705) Mathematician, born in Basel, Switzerland, the brother of Johann Bernoulli. He became professor of mathematics at Basel in 1687. He investigated infinite series, the cycloid, transcendental curves, the logarithmic spiral, and the catenary. In 1690 he applied Gottfried Leibniz's newly discovered differential calculus to a problem in geometry, first using the term *integral*. His *Ars conjectandi* (1713) was an important contribution to probability theory. |