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1580 
Leiden, Netherlands 
30 Oct 1626 
Leiden, Netherlands 
Willebrord Snell studied law at the University of Leiden but was very interested in mathematics and taught mathematics even while he studied law. From about 1600 he travelled to various European countries, mostly discussing astronomy. In 1602 he went to Paris where his studies continued. He received his degree from Leiden in 1607. Snell's father, Rudolph Snell (15461613), was professor of mathematics at Leiden and, in 1604, Willebrord visited Switzerland with his father. In 1613 he succeeded his father as professor of mathematics at the University of Leiden. In 1617 Snell published Eratosthenes Batavus, which contains his methods for measuring the Earth. He proposed the method of triangulation and this work is the foundation of geodesy. Snell also improved the classical method of calculating approximate values of π by polygons. Using his method 96 sided polygons give π correct to 7 places while the classical method yields only 2 places. van Ceulen 's 35 places could be found with polygons of 2^{30} sides rather than 2^{62}. Although he discovered the law of refraction , a basis of modern geometric optics, in 1621, he did not publish it and only in 1703 did it become known when Huygens published Snell's result in Dioptrica. Snell also discovered the sine law. Snell studied the loxodrome , the path on the sphere that makes constant angle with the meridians. This appears in Tiphys batavus published in 1624, a work in which he studied navigation.
Source:School of Mathematics and Statistics University of St Andrews, Scotland
