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- Nicole d'Oresme (ca. 1320 - 1382)
- Born in France.
- He introduced a mathematical methodology which eventually developed into analytical geometry.
- He suggested the possibility of irrational proportion.
- William Oughtred (1575-1660)
- Born in England.
- He introduced the symbol x for multiplication and the symbol of : : in proportion.
- He introduced the abbreviations for such tems as sine, cosine, tangent, cotangent, secant, and cosecant.
