Jacob Bernoulli (6 January 1655 – 16 August 1705) was a Swiss mathematician who was the first to use the term integral. He studied the catenary, the curve of a suspended string. He was an early user of polar coordinates and discovered the isochrone.

The scion of a family of drug merchants, Jakob Bernoulli was compelled to study theology but became interested in mathematics despite his father’s opposition. His travels led to a wide correspondence with mathematicians. Refusing a church appointment, he accepted a professorial chair of mathematics at the University of Basel in 1687; and, following his mastery of the mathematical works of John Wallis, Isaac Barrow (both English), René Descartes (French), and G.W. Leibniz, who first drew his attention to calculus, he embarked upon original contributions. In 1690 Bernoulli became the first to use the term integral in analyzing a curve of descent. His 1691 study of the catenary, or the curve formed by a chain suspended between its two extremities, was soon applied in the building of suspension bridges. In 1695 he also applied calculus to the design of bridges. During these years, he often engaged in disputes with his brother Johann Bernoulli over mathematical issues.

Bio:https://www.britannica.com/biography/Jakob-Bernoulli
https://mathshistory.st-andrews.ac.uk/Biographies/Bernoulli_Jacob/