TIKZ/PGF

\documentclass{article}
\usepackage{tikz,ifthen,fullpage}

\begin{document}
\thispagestyle{empty}
\begin{tikzpicture}
\def\a{12}\def\couleur{black}
	\path[coordinate] (0 cm,0 cm)   coordinate(A)%
	                  (\a cm,0 cm)  coordinate(B)%
	                  (\a cm,\a cm) coordinate(C)%
	                  (0 cm,\a cm)  coordinate(D);%
\draw[fill=\couleur] (A)--(B)--(C)--(D)--cycle;
\foreach \i in {2,3,...,14}
{\ifthenelse{\isodd{\i}}{\def\couleur{black}}{\def\couleur{red}}
\node(E) at (A){};
\path (A)--(B) node[pos=.75] (A){}
         --(C) node[pos=.75] (B){}
         --(D) node[pos=.75] (C){}
         --(E) node[pos=.75] (D){};
\draw[fill=\couleur] (A.center)--(B.center)--(C.center)--(D.center)--cycle;}
\end{tikzpicture}
\end{document}

% blackboard
% Author: Alain Matthes
\documentclass{article}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{tikz,fullpage}
\usetikzlibrary{backgrounds}

 \begin{document}
    \thispagestyle{empty}
    \tikzstyle{background rectangle}=[fill=black]
    \scalebox{0.75}{%
    \begin{tikzpicture}[show background rectangle,line width = 1pt]
    \draw[fill=white] (0,0) circle(2pt);
    \draw[color=white] (0,0) circle(5cm)node[](O){};
    \draw[color=white] (0,0) -- (-140:5) node(A){$\bullet$};
    \path[anchor=base] (O) to node[midway,sloped,color=white]{Rayon} (A);
    \draw[anchor=base,color=white] (A.center) -- +(130:5) ;
    \draw[anchor=base,color=white] (A.center) -- +(-50:5)%
          node[pos=0.5,sloped] {Tangente};
    \end{tikzpicture}}

 \end{document}

% suite
% Author: Alain Matthes
\documentclass{article}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{tikz,fp,ifthen,fullpage}


\begin{document}
  \thispagestyle{empty}
\begin{figure}[htbp]
    \centering
    \newcommand{\x}{.4} 
    \begin{tikzpicture}[scale=10]  
    \draw[color=blue] plot[id=cosinus,domain=0:1]%
          function{cos(x)} node[right] {};
    \draw[color=red](0,0)--(1,1);
    \draw[->,>=latex](0,0)--(0,1);
    \draw[->,>=latex](0,0)--(1,0);
    \newcounter{cnt}
    \FPset\x{0.2}
    \setcounter{cnt}{0}
       \whiledo{\value{cnt}<8}{%
          \FPeval{\y}{cos(x)}% 
          \draw[color=red] (\x,\x){};
          \draw[color=red](\x,\y){} ;
          \draw[color=blue](\x,\x)--(\x,\y)--(\y,\y);
          \draw[color=orange,dotted,line width=0.8pt]%
               (\x,\x)--(\x,0) node[below=8pt]{$u_\thecnt$} ;
          \stepcounter{cnt}
          \draw[color=blue,dotted,line width=0.8pt]%
               (\x,\y)--(0,\y) node[left=8pt] {$u_\thecnt$} ;
          \let\x\y}
    \end{tikzpicture}
    \caption{$f(x)=\cos (x)$}
\end{figure}
 \end{document}