**Simon Stevin** was a Flemish mathematician who presented the first elementary and thorough account of decimal fractions and introduced their use in mathematics.

- Nothing is known of Simon's early years or of his education although one assumes he was brought up in the Calvinist tradition.
- Stevin became a bookkeeper and cashier with a firm in Antwerp.
- Stevin's move to the north Netherlands certainly coincided with their move to independence from the King of Spain.
- Certainly Stevin was not alone in fleeing from the south Netherlands around this time, with many going to the north, but others fleeing to England or Germany.
- While Stevin was at the University of Leiden he met Maurits (Maurice), the Count Of Nassau, who was William of Orange's second son.
- The two became close friends and Stevin became mathematics tutor to the Prince as well as a close advisor.
- With Prince Maurits now head of the army of the republic, and with Stevin as an advisor in his service, a series of military triumphs over the Spanish forces followed.
- In 1600 he asked Stevin to set up an engineering school within the University of Leiden.
- Certainly Prince Maurits saw his friend Stevin as having major importance in his success and the recent discovery of a journal in the Public Record Office of The Hague recording Stevin's salary as 600 Dutch guilders in 1604 confirms his high position.
- It is believed that from 1604 Stevin was quartermaster-general of the army of the States-General.
- Stevin bought a house at the Raamstraat in The Hague in 1612 for 3800 Dutch guilders (another sign of his high status and wealth).
- The author of 11 books, Simon Stevin made significant contributions to trigonometry, mechanics, architecture, musical theory, geography, fortification, and navigation.
- Before presenting the numerical tables, Stevin gave rules for simple and compound interest and also gave many examples of their use.
- In Problemata geometrica Ⓣ(Gemetrical problems) (1583) Stevin presented geometry based largely on Euclid and Archimedes but the problems which he studied show that he was also influenced by Dürer.
- Stevin gave an interesting account in this work of constructions related to polygons and polyhedra, using the concept of similarity, and a study of regular and semi-regular polyhedra.
- Although he did not invent decimals (they had been used by the Arabs and the Chinese long before Stevin's time) he did introduce their use in mathematics in Europe.
- Stevin states that the universal introduction of decimal coinage, measures and weights would only be a matter of time (but he probably would be amazed to know that in the 21st century some countries still resist adopting decimal systems).
- Stevin's notation was to be taken up by Clavius and Napier and it developed into that used today.
- In the latter Stevin presented a unified treatment for solving quadratic equations and a method for finding approximate solutions to algebraic equations of all degrees.
- Stevin's notion of a real number was accepted by essentially all later scientists.
- Particularly important was Stevin's acceptance of negative numbers but he did not accept the 'new' imaginary numbers and this was to hold back their development.
- Inspired by Archimedes, Stevin wrote important works on mechanics.
- Although he undertook his mathematical work earlier in his life, Stevin collected together some of his mathematical writings which he edited and published during the years 1605 to 1608 in Wiskonstighe Ghedachtenissen Ⓣ(Mathematical Memoirs) (Mathematical Memoirs).
- Stevin, in his book Stelreghel Ⓣ(Algebra) used the notation +, - and √.
- In Het Burgherlick leven Ⓣ(The life of a citizen) Stevin discusses how a citizen of a state should comply with the rules of the authorities (even when they appear unjust) and, in particular, he advises citizens how to behave in times of civil unrest.
- In De Sterktenbouwing Ⓣ(The Strength Bouwing) Stevin takes an Italian method of fortification and modifies it for Dutch use.
- In the first of the final double work that we mentioned above, Stevin describes the establishment, layout and setting up of a military camp.
- The second of the two works deals with sluices Stevin had designed to put into fortifications to keep a moat at the correct depth.

Born 1548, Bruges, Burgundian Netherlands (now Belgium). Died February 1620, The Hague, Dutch Republic (now Netherlands).

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Analysis, Astronomy, Origin Belgium, Special Numbers And Numerals

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