Jean-François Callet

Jean-François Callet (25 October 1744 – 14 November 1798) was a French professor of mathematics who wrote an influential book of logarithm tables and taught spherical trigonometry and navigation.

Callet was born in Versailles and became a professor of hydrographic engineering. Callet's most influential work was a portable table of logarithms (based on the work of William Gardiner) ''Tables Portatives de Logarithmes'' published in 1795 which went into many editions until 1906. It has fifty pages with logarithms of the sine, cosine and tangent, as well as natural sines and cosines. It was influential and led to other improved logarithm tables such as those of Edward Sang. Another work of his was a spherical trigonometric text for use in navigation published in 1798. It was made in collaboration with instrument maker Jean François Richer who was attempting to create a navigation instrument called the trigonometric circle or ''Compas Trigonométrique'' in his application for the Abbe Raynal Prize which sought a reliable and accurate method for the reduction of the apparent to the true distance between two stars. This would be usable to determine the longitude of the ship's position. Richer's application won the 1791 price. Provided by Wikipedia