**Adriaan van Roomen** or **Adrianus Romanus** was a Flemish mathematician who calculated $\pi$ to 16 decimal places using Archimedes' method.

- After studying ancient languages in his hometown, van Roomen studied mathematics and philosophy at the Jesuit College in Cologne.
- Van Roomen was professor of mathematics and medicine at Leuven from 1586 to 1592 and, for six months during 1592, he was rector of the University.
- In Chapters 10 and 11 van Roomen would study the circle.
- In 1591, van Roomen published Ouranographia.
- After these years in Leuven, van Roomen went to Würzburg where again he was appointed professor of medicine giving his first lecture on 17 May 1593.
- Van Roomen's appointment by Prince Bishop Julius Echter von Mespelbrunn was officially confirmed on the last day of August 1593.
- It is likely that van Roomen was glad to have an opportunity to leave the Netherlands since there was much unrest and fighting over the Spanish held territory.
- Although he was employed as a professor of medicine, it was mathematics that was van Roomen's real love.
- Van Roomen had proposed a problem which involved solving an equation of degree 45 in Ideae mathematicae (1593).
- Van Roomen solved it using two hyperbolas, publishing the result in 1596.
- A dispute with the French scholar Josephus Justus Scaliger (1540-1609) prompted van Roomen to publish further works.
- Van Roomen bought Scaliger's pamphlet on squaring the circle from a book fair in Frankfurt in the autumn of 1594.
- He sent a copy to van Roomen in March 1595.
- Van Roomen decided to publish a work defending Archimedes from Scaliger's attacks.
- Van Roomen's response was the three-part book In Archimedis Circuli Dimensionem Expositio et Analysis (1597).
- The first part contains a Latin translation by van Roomen of the Greek text of Archimedes' On the measurement of the circle.
- Van Roomen proposes unifying geometry and arithmetic under his concept of 'mathesis universalis'.
- The third part of van Roomen's 1597 work, consisting of ten dialogues, points out the errors in Scaliger's attempt to square the circle and also points out the errors in the works of several other mathematicians including Oronce Fine who had made similar claims.
- During the ten years 1593-1603 that van Roomen spent in Würzburg he supervised the dissertations of twenty students which were printed by the local printer Georgius Fleischmann.
- In 1603 van Roomen gave up his duties as professor at Würzburg, requesting permission from Prince Bishop Julius to travel to Leuven on 19 March 1603.
- The reason for this request was that van Roomen had been invited to the Zamoyski Academy in Zamosc, Poland.
- We have accurate details of van Roomen's travels from Würzburg to Zamosc preserved in the diary of the Polish mathematician Jan Brozek (1585-1652), also known as Ioannes Broscius or Johannes Broscius, who worked at Kraków Academy (now the Jagiellonian University).
- He noted the days that van Roomen spent in Kraków in his travels between Würzburg and Zamosc.
- Van Roomen arrived in Kraków on 24 August 1611 after spending about a year in Zamosc.
- It is clear that by this time van Roomen was sufficiently concerned about his health that, in 1613, he travelled to Leuven where he made a will.
- Van Roomen died in Mainz while on a journey from Leuven to Würzburg.
- One of van Roomen's most impressive results was finding π to 16 decimal places.
- Van Roomen's interest in π was almost certainly as a result of his friendship with Ludolph van Ceulen.
- Van Roomen worked on trigonometry and the calculation of chords in a circle.
- In 1600 van Roomen visited Prague where he met Johannes Kepler and told him of his worries about the methods employed in Rheticus's trigonometric tables.
- Among other contributions made by van Roomen was one to figures of equal perimeter.
- Van Roomen generalised the results of Pappus and, again showing his precise thinking, realised that 'regular' had not been properly defined.

Born 29 September 1561, Leuven, Spanish Netherlands (now Belgium). Died 4 May 1615, Mainz, Germany.

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Astronomy, Origin Belgium, Number Theory, Special Numbers And Numerals

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive