William Oughtred, also Owtred, Uhtred, etc., was an English mathematician and Anglican clergyman. After John Napier invented logarithms and Edmund Gunter created the logarithmic scales upon which slide rules are based, Oughtred was the first to use two such scales sliding by one another to perform direct multiplication and division. He is credited with inventing the slide rule in about 1622. He also introduced the "×" symbol for multiplication and the abbreviations "sin" and "cos" for the sine and cosine functions.
William Oughtred engraving by Wenceslaus Hollar
The Caryll home at Great Tangley
Old St Peter and St Paul's Church, Albury, Surrey, where William Oughtred was rector from 1610 to 1660, and where he is buried.
An instrument for Oughtred's "Circles of Proportion", by Elias Allen, c. 1633-1640 (Harvard University, Putnam Gallery)
In mathematics, the logarithm is the inverse function to exponentiation. That means that the logarithm of a number x to the base b is the exponent to which b must be raised to produce x. For example, since 1000 = 103, the logarithm base of 1000 is 3, or log10 (1000) = 3. The logarithm of x to base b is denoted as logb (x), or without parentheses, logb x. When the base is clear from the context or is irrelevant, such as in big O notation, it is sometimes written log x.
The logarithm keys (LOG for base 10 and LN for base e) on a TI-83 Plus graphing calculator
A nautilus shell displaying a logarithmic spiral