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'Pierre Frédéric Sarrus' (10 March 1798, Saint-Affrique - 20 November 1861) was a French mathematician.
Sarrus was professor at the University of Strasbourg, France (1826-1856) and member of the Academy of Sciences in Paris (1842).
He is author of several treaties, including one on the solution of numeric equations with multiple unknowns (1842); one on multiple integrals and their integrability conditions; one on the determination of the orbits of the comets. He also discovered a mnemonic rule for solving the determinant of a 3-by-3 matrix, named Sarrus' scheme, which provides an easy-to-remember method of working out the determinant of a 3-by-3 matrix (as illustrated in "cross product"). Sarrus also demonstrated the fundamental lemma of the calculus of variations.
Sarrus numbers are pseudoprimes to base 2.