Benedict Irwin edited Polters.tex  over 9 years ago

Commit id: 1a9bffbe6708fa27fba0ec0a4e6551c9c4b20cf7

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/a_2 a_3\backslash /b_2 b_3\backslash = a_1b_1+a_2b_2+a_3b_3  \end{equation}  The cross product makes a different sense in this format \begin{equation}  \hspace{67pt}/a_1 \backslash \times/b_1\backslash \hspace{45pt} (a_2b_3-a_3b_2)\hspace{95pt}\\  /a_2 a_3\backslash \hspace{5pt} /b_2 b_3\backslash = (a_3b_1-a_1b_3) (a_1b_2-a_2b_1)  \end{equation}  Where the triangle like frame is beginning to be ommited. However the result on the right hand side as a new three vector can now be explained by the sentence: "the element at a position is the anti-clockwise element of LH operand times clockwise element of RH operand minus clockwise element of LH operand times anti-clockwise element of RH operand". Bit of a mouthfull, but there is order here. Actually, if we define the index as having a modulo count on, such that elements 4 and 1 are equivalent then we can state the cross product as \begin{equation}  (a \cross b)_i = a_{i+1}b_{i-1}-a_{i-1}b_{i+1}  \end{equation}  Which is an alternate definition. Much more concise, only uses one index.