\documentclass[oneside,12pt]{book}
\usepackage[top=30mm,bottom=30mm,left=25mm,right=35mm]{geometry}
\usepackage{wrapfig}
\usepackage{marginnote}
\usepackage{amssymb,amsmath}
\usepackage{fancyhdr}
\usepackage{graphicx}
\usepackage{tikz}
\usepackage{verbatim}

\usetikzlibrary{arrows}

% بسته‌‌ای برای ظاهر شدن شکل‌ها و تصاویر متن
\usepackage{graphicx}
\usepackage{xepersian}

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%دستور زیر برای تعیین فونت اعداد می‌باشد
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


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\begin{document}
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\chapter{اعداد مختلط}
\begin{example}
فرم مثلثاتی اعداد مختلط زیر را همین جا مشخص کنید:
 $$z=-5+5i$$\\
\begin{wrapfigure}{l}{0.3\textwidth}
\begin{tikzpicture}[ scale=2]
 % axis
 \draw[axis][->] (-1.1,0)  -- (1.1,0) node(xline)[right]
        {$X$};
\draw[axis] [->](0,-1.1) -- (0,1.1) node(yline)[above] {$Y$};
\draw[dashed] (-0.4,0) -- (-0.4,0.4);
\draw[dashed] (0,0.4) -- (-0.4,0.4);
\fill[red] (-0.4,0.4) circle (0.5pt);
 \draw (0,0) -- (-0.4,0.4);
 \coordinate [label=above:\textcolor{red}{$z(-5,5)$}] (A) at (-0.4,0.4);
 \draw[dashed] (yaxis |- A) node[right] {$5$}
        -| (xaxis -| A) node[below] {$-5$};
 \end{tikzpicture}    
\end{wrapfigure}
$$x=-5\quad,\quad y=5\Rightarrow r=\sqrt{50}$$
$$\tan\theta =-1\Rightarrow\theta =\frac{3\pi}{4}\quad\Rightarrow z=rcis\theta=5\sqrt{2}cis\frac{3\pi}{4}$$\\



\end{document}