Adriaan van Roomen, Flemish priest and mathematician (b. 1561)
Adriaan van Roomen (29 September 1561 – 4 May 1615), also known as Adrianus Romanus, was a mathematician, professor of medicine and medical astronomer from the Duchy of Brabant in the Habsburg Netherlands who was active throughout Central Europe in the late 16th and early 17th centuries. As a mathematician he worked in algebra, trigonometry and geometry; and on the decimal expansion of π. He solved the Problem of Apollonius using a new method that involved intersecting hyperbolas. He also wrote on the Gregorian calendar reform.