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How did the convention of 'multiplying' using the cross symbol $4\times 3$ become $4\cdot 3$, using a dot in the middle?

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    $\begingroup$ x looks to much like a $x$ ? $\endgroup$ – user392395 Jun 17 '17 at 17:32
  • $\begingroup$ See also the similar Question at History of Science and Mathematics (HSM.SE). $\endgroup$ – hardmath Jun 17 '17 at 17:39
  • $\begingroup$ Note, that it often changes further, using juxtaposition so that we use $xy$ to mean $x\cdot y = x\times y$ when it is clear, in the context, what the multiplicative operation is. E.g., Matrices: AB means the matrix $A \cdot B$, where the operation is matrix multiplication. Similarly $3x^2 = 3\cdot x\cdot x$. The symbol $\times$ becomes more useful as representing the Cartesian Product of sets, as cross-product, and by giving dimensions: e.g. a matrix $A_{2\times 2}$, or of a square: $x\times x$, etc.. $\endgroup$ – amWhy Jun 17 '17 at 17:59
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As far as I know this originated from Leibniz around 1695 because he thought that you could too easily mistake the multiplying symbol $\times$ for the variable $x$ and he used a point instead. He first used it in a correspondence in 1698.

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From A Brief History of Algebraic Notation by Lynn Stallings:

Textbook writer William Oughtred...was the first to use the St. Andrew's Cross, $\times$, for multiplication in his 1631 Clavis Mathimaticae...Seventeenth century German genius Leibniz criticized Oughtred's use of the cross...because it looked too much like the letter $x$; he suggested the $\cdot$ for multiplication in its place.

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