The Key to Mathematics. This work, known in Latin as 'Clavis Mathematicae', is by the English mathematician William Oughtred (1575-1660) and represents algebraic knowledge at the time. Oughtred argued for the more widespread use of symbols in mathematics and introduced a number of mathematical symbols, such as the 'x' for multiplication and the sin and cos notation for trigonometry. This page is from the first English edition, published in 1647 in London.
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