Question2: Trouver le centre et rayon du cercle inscrit au triangle

📅 February 08, 2024   |   👁️ Views: 345


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maths Exercise for questions-and-answers PDF preview

\documentclass[12pt,a4paper]{article}
\usepackage{tabularx}
\usepackage{booktabs}
\usepackage{ragged2e}
\usepackage[left=1.00cm, right=1.00cm, top=0.50cm, bottom=1.00cm]{geometry}
\usepackage{amsmath,amsfonts,amssymb}
\usepackage{mathrsfs}
\usepackage{enumitem}
\usepackage{multirow}
\usepackage{adjustbox}
\usepackage{xcolor}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{calc}
\usepackage[ddmmyyyy]{datetime}

\usepackage{setspace}

\usepackage{hyperref}
\hypersetup{
    colorlinks=true,
    linkcolor=blue
}
\newcommand{\mylink}{\href{https://mosaid.xyz/cc}{www.mosaid.xyz}}

\newcolumntype{C}{>{\Centering\arraybackslash}X}

\begin{document}
\thispagestyle{empty}
\noindent
\begin{center}
    \begin{tabular}{@{}p{0.22\textwidth}p{0.57\textwidth}p{0.17\textwidth}}
        %\toprule
            \multirow{2}{*}{\parbox{\linewidth}{Prof MOSAID \newline \mylink }}
            & \Centering
            {Centre et Rayon du Cercle Inscrit d'un Triangle}
            & \hfill   \\
        \bottomrule
    \end{tabular}
\end{center}

\section{Le centre}

\begin{minipage}[T]{0.7\linewidth}
\noindent Le centre du cercle inscrit est le point d'intersection des trois médianes du triangle.
Ce point est  aussi le centre de gravité du triangle.\\ autrement dit, le barycentre des sommets du triangle
\(ABC\).
\[G=\text{bar}\{(A,BC),(B,AC),(C,AB)\}\]
\end{minipage}
\begin{minipage}[T]{0.3\linewidth}
    \begin{tikzpicture}
    % Coordonnées des sommets du triangle
    \coordinate (A) at (0,0);
    \coordinate (B) at (3,0);
    \coordinate (C) at (1.5,2);

    % Dessin du triangle
    \draw (A) -- (B) -- (C) -- cycle;

    % Coordonnées des milieux des côtés du triangle
    \coordinate (MAB) at ($(A)!0.5!(B)$);
    \coordinate (MAC) at ($(A)!0.5!(C)$);
    \coordinate (MBC) at ($(B)!0.5!(C)$);

    % Dessin des médianes
    \draw[red] (A) -- (MBC);
    \draw[red] (B) -- (MAC);
    \draw[red] (C) -- (MAB);

    % Point d'intersection des médianes
    \coordinate (G) at (intersection of A--MBC and B--MAC);

    % Marquage des sommets et du point d'intersection
    \foreach \point in {A,B,C,G}
        \filldraw [black] (\point) circle (2pt);

    % Étiquetage des sommets
    \node [below left] at (A) {$A$};
    \node [below right] at (B) {$B$};
    \node [above] at (C) {$C$};
    \node [above right] at (G) {$G$};

\end{tikzpicture}
\end{minipage}\\
chaque sommet est un point pondéré de coefficient; la
langueur du côté opposé.\\
Les coordonnées de \(G\) sont données par la formule :
\[\mathbf{x_G = \frac{BC \cdot x_A + AC \cdot x_B + AB \cdot x_C}{BC + AC + AB}}
    \quad\text{et}\quad
\mathbf{y_G = \frac{BC \cdot y_A + AC \cdot y_B + AB \cdot y_C}{BC + AC + AB}}\]

\section{Le rayon}
Le rayon du cercle inscrit au triangle \(ABC\) est définit par la formule
\(\mathbf{r = \frac{2A}{AB + AC + BC} }\).\\où \(A\) est l'aire du triangle.\\
\begin{tabular}{@{}p{0.35\textwidth}p{0.58\textwidth}}
    \textbf{L'aire avec le produit vectoriel}: &
    \(A=\frac{1}{2}\|\overrightarrow{BA}\land\overrightarrow{BC}\|\)\\
    \textbf{L'aire avec le determinant:}&
    \(A=\frac{1}{2}|det(\overrightarrow{BA},\overrightarrow{BC})|\)\\
    \textbf{L'aire avec la formule de Héron:} & \( A = \sqrt{s(s-AB)(s-AC)(s-BC)} \).\\
    &avec  \( s = \frac{AB + AC + BC}{2} \) est la moitié du périmètre du triangle.\\
\end{tabular}\\
\\
\\
En utilisant ces formules, vous pouvez trouver le centre et le rayon du cercle inscrit pour n'importe quel triangle.
\section{Application:}
\begin{adjustbox}{valign=t}
\begin{minipage}[t]{0.48\linewidth}
\setstretch{1.5}
Soient les points A(2,4), B(5,1) et C(7,8)\\
- \( \overrightarrow{AB}(3,-3)\), \( \overrightarrow{BC}(2,7)\)
et \( \overrightarrow{AC}(5,4)\)\\
- \( AB = 3\sqrt{2} \), \( BC = \sqrt{53} \) et \( AC = \sqrt{41} \) \\
- \( A = 13.5 \), \( s \simeq 8.96 \) \\
La figure si contre utilise ces forumles pour \\determiner le rayon et centre du cercle inscrit.
\end{minipage}
\end{adjustbox}
\hfill
\begin{adjustbox}{valign=t}
\begin{minipage}[t]{0.50\linewidth}
\centering
\begin{tikzpicture}

    % Define the coordinates of the triangle
    \coordinate[label=above:$A$] (A) at (2, 4);
    \coordinate[label=below:$B$] (B) at (5, 1);
    \coordinate[label=above right:$C$] (C) at (7, 8);

    % Draw the triangle
    \draw (A) -- (B) -- (C) -- cycle;

    % Calculate the lengths of the sides
    \pgfmathsetmacro{\BC}{veclen(5-7,1-8)} % Length of side BC
    \pgfmathsetmacro{\AC}{veclen(2-7,4-8)} % Length of side AC
    \pgfmathsetmacro{\AB}{veclen(2-5,4-1)} % Length of side AB

    % Calculate the semi-perimeter
    \pgfmathsetmacro{\s}{(\BC + \AC + \AB) / 2}

    % Calculate the area using Heron's formula
    \pgfmathsetmacro{\area}{sqrt(\s * (\s - \BC) * (\s - \AC) * (\s - \AB))}

    % Calculate the coordinates of the incenter
    \pgfmathsetmacro{\incenterX}{(\BC * 2 + \AC * 5 + \AB * 7) / (\BC + \AC + \AB)}
    \pgfmathsetmacro{\incenterY}{(\BC * 4 + \AC * 1 + \AB * 8) / (\BC + \AC + \AB)}
    \coordinate (G) at (\incenterX, \incenterY);

    % Calculate the perimeter
    \pgfmathsetmacro{\perimeter}{\BC + \AC + \AB}

    % Calculate the radius of the inscribed circle
    \pgfmathsetmacro{\radius}{2 * \area / \perimeter}

    % Draw the inscribed circle
    \fill[red] (G) circle (2pt) node[above right] {G};
    \draw (G) circle (\radius );

    % Print out the radius for debugging
    \node at (current bounding box.south) [below] (AA) {r = \radius, A = \area, s = \s};
    % Print out the coordinates of I for debugging
    \node at (AA.south) [below] (BB) {Coordonnées de \(G\): (\incenterX, \incenterY)};
\end{tikzpicture}
\\
\vspace*{1cm}
\end{minipage}
\end{adjustbox}\\
\textcolor{white}{.}\hfill \underline{MOSAID le \today}\\
\textcolor{white}{.}\hfill \mylink

\end{document}

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