Commit 6a6b3d62 authored by Claude Meny's avatar Claude Meny

Update cheatsheet.fr.md

parent 80ba9696
Pipeline #16456 canceled with stage
......@@ -54,47 +54,52 @@ valeurs et vecteurs propres
Soit $`M`$ une matrice réelle carré de dimension $`m\times m`$.
Par définition : $`\forall k\in \mathbb{N}^{\*}\,,\,`$ **$`\mathbf{M^k = \underbrace{M \times M \times \cdots \times M}_{\color{blue}{\text{k fois}}}`$**
Par définition : $`\forall k\in \mathbb{N}^{*}\,,\,`$
**$`\mathbf{M^k = \underbrace{M \times M \times \cdots \times M}_{\color{blue}{\text{k fois}}}}`$**
##### $`M`$ est diagonale`$
<br>
*$`\mathbf{M^2}`$* $`\; = M\times M`$
$`\quad \begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}\;\times\;\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}`$
$`\quad = \begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}\;\times\;\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}`$
*$`\mathbf{\quad \begin{pmatrix} \lambda_1^2 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^2\\ \end{pmatrix}}`$*
*$`\mathbf{\quad = \begin{pmatrix} \lambda_1^2 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^2\\ \end{pmatrix}}`$*
Et par récurrence,
$`\forall k \in \mathbb{N}^{\*}\setminus \{1}`$
$`\forall k \in \mathbb{N}^{*}\{1}`$ <!--\setminus -->
**$`\mathbf{M^k}`$** $`\; = M^{k-1}\times M`$
$`\quad = \begin{pmatrix} \lambda_1^{k-1} & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^{k-1} \\ \end{pmatrix}\;\times\; \begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}`$
**$`\mathbf{\quad = \begin{pmatrix} \lambda_1^k & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^k\\ \end{pmatrix}}`$
**$`\mathbf{\quad = \begin{pmatrix} \lambda_1^k & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^k\\ \end{pmatrix}}`$**
##### $`M`$ est non diagonale, mais diagonalisable`$
<br>
*$`\mathbf{M^2}`$* $`\; = M\times M`$
$`\quad P\,\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}\,\underbrace{P^{-1}\;\times\;
$`\quad = P\,\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}\,\underbrace{P^{-1}\;\times\;
\; P}_{\color{blue}{= I_m}}\,\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}\,P^{-1}`$
$`\quad P\,\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}^{\,2}\,\underbrace{P^{-1}`$
$`\quad = P\,\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m \\ \end{pmatrix}^{\,2}`$
*$`\mathbf{\quad P\,\begin{pmatrix} \lambda_1^2 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^2\\ \end{pmatrix}\,\underbrace{P^{-1}}`$*
*$`\mathbf{\quad = P\,\begin{pmatrix} \lambda_1^2 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^2\\ \end{pmatrix}\,\underbrace{P^{-1}}`$*
Et par récurrence :
$`\forall k \in \mathbb{N}^{\*}\setminus \{1}`$
$`\forall k \in \mathbb{N}^{\*}\ {1}`$
**$`\mathbf{M^k}`$** $`\; = M^{k-1}\times M`$
$`\quad = P\,\begin{pmatrix} \lambda_1^{k-1} & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^{k-1} \\ \end{pmatrix}\,\underbrace{P^{-1}\;\times\; P}_{\color{blue}{= I_m}}\,\begin{pmatrix} \lambda_1 & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m\\ \end{pmatrix}\,P^{-1}`$
**$`\mathbf{\quad P\,\begin{pmatrix} \lambda_1^k & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^k\\ \end{pmatrix}\,\underbrace{P^{-1}}`$**
**$`\mathbf{\quad = P\,\begin{pmatrix} \lambda_1^k & 0 & 0 \\ 0 & \cdots & 0 \\ 0 & 0 & \lambda_m^k\\ \end{pmatrix}\,\underbrace{P^{-1}}`$**
<br>
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