Pierre Frédéric Sarrus (10 March 1798, Saint-Affrique - 20 November 1861) was a French mathematician. Sarrus was professor at the University of Strasbourg, France (1826-1856) and member of the Academy of Sciences in Paris (1842). He discovered a mnemonic rule for solving the determinant of a 3-by-3 matrix, named Sarrus' scheme, which provides an easy-to-remember method of working out the determinant of a 3-by-3 matrix.
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% Mnemonic rule for matrix determinant % Author: Alain Matthes \documentclass[]{article} \usepackage[utf8]{inputenc} \usepackage[upright]{fourier} \usepackage{tikz} \usepackage[active,tightpage]{preview} \PreviewEnvironment{tikzpicture} \setlength\PreviewBorder{5pt}% \usetikzlibrary{matrix} \usepackage{fullpage,amsmath} \begin{document} Pierre Frédéric Sarrus (10 March 1798, Saint-Affrique - 20 November 1861) was a French mathematician. Sarrus was professor at the University of Strasbourg, France (1826-1856) and member of the Academy of Sciences in Paris (1842). He discovered a mnemonic rule for solving the determinant of a 3-by-3 matrix, named Sarrus' scheme, which provides an easy-to-remember method of working out the determinant of a 3-by-3 matrix (as illustrated below) \tikzset{node style ge/.style={circle}} det(M)= $\left| \begin{matrix} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33} \\ \end{matrix}% \right|$ =$\big(a_{11}a_{22}a_{33}+a_{21}a_{32}a_{13}+a_{31}a_{12}a_{33}\big)-\big(a_{13}a_{22}a_{31}+a_{23}a_{32}a_{11}+a_{33}a_{12}a_{31}\big)$ \begin{tikzpicture}[baseline=(A.center)] \tikzset{BarreStyle/.style = {opacity=.4,line width=4 mm,line cap=round,color=#1}} \tikzset{SignePlus/.style = {above left,,opacity=1,circle,fill=#1!50}} \tikzset{SigneMoins/.style = {below left,,opacity=1,circle,fill=#1!50}} % les matrices \matrix (A) [matrix of math nodes, nodes = {node style ge},,column sep=0 mm] { a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33} \\ a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{13}\\ }; \draw [BarreStyle=blue] (A-1-1.north west) node[SignePlus=blue] {$+$} to (A-3-3.south east) ; \draw [BarreStyle=blue] (A-2-1.north west) node[SignePlus=blue] {$+$} to (A-4-3.south east) ; \draw [BarreStyle=blue] (A-3-1.north west) node[SignePlus=blue] {$+$} to (A-5-3.south east) ; \draw [BarreStyle=red] (A-3-1.south west) node[SigneMoins=red] {$-$} to (A-1-3.north east); \draw [BarreStyle=red] (A-4-1.south west) node[SigneMoins=red] {$-$} to (A-2-3.north east); \draw [BarreStyle=red] (A-5-1.south west) node[SigneMoins=red] {$-$} to (A-3-3.north east); \end{tikzpicture} \end{document}
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