
\begin{tabular}{l@{~}|@{~}l}
\begin{minipage}{\dimexpr\linewidth-5cm}
Construisons en premier le point L en prolongeant les segments [IJ] et [CB] de sorte à tracer les demi-droites [IJ) et [CB) comme ci-dessous :
\end{minipage}
&
\begin{minipage}{5cm}
\begin{center}
\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (3,0);
\coordinate (C) at (3,3);
\coordinate (D) at (0,3);
\coordinate (E) at (1,1);
\coordinate (F) at (4,1);
\coordinate (G) at (4,4);
\coordinate (H) at (1,4);
\coordinate (I) at (0,1.5);
\coordinate (J) at (1.5,0);
\coordinate (K) at (4,3);
\shade[left color=purple!5,right color=purple!40] (I) node[left] {I} -- (J) node[below] {J} -- (K) node[right] {K} -- cycle;
\draw[purple] (I) -- (J);
\draw[dashed,purple] (I) -- (K) -- (J);
\draw (A) node[below left] {A} -- (B) node[below right] {B} -- (C) node[above] {C} -- (D) node[above left] {D} -- (H) node[above] {H} -- (G) node[above right] {G} -- (F) node[right] {F} -- (B);
\draw (A) -- (D);
\draw (C) -- (G);
\draw[dashed] (A) -- (E) -- (H);
\draw[dashed] (E) node[above right] {E} -- (F);
%
\draw[dotted,gray] (B) -- (3,-2);
\draw[dotted,gray] (J) -- (3.5,-2);
\fill[red] (3,-1.5) circle (1.5pt) node[right] {L};
\end{tikzpicture}
\end{center}
\end{minipage}
\\
\begin{minipage}{\dimexpr\linewidth-5cm}
Les points L et K appartiennent aux plans (IJK) et à la face (CBFG), par conséquent, l'intersection de ces deux plans est la droite (LK). On la trace donc et on trace en rouge le segment qui est dans la face (CBFG) :
\end{minipage}
&
\begin{minipage}{5cm}
\begin{center}
\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (3,0);
\coordinate (C) at (3,3);
\coordinate (D) at (0,3);
\coordinate (E) at (1,1);
\coordinate (F) at (4,1);
\coordinate (G) at (4,4);
\coordinate (H) at (1,4);
\coordinate (I) at (0,1.5);
\coordinate (J) at (1.5,0);
\coordinate (K) at (4,3);
\shade[left color=purple!5,right color=purple!40] (I) node[left] {I} -- (J) node[below] {J} -- (K) node[right] {K} -- cycle;
\draw[purple] (I) -- (J);
\draw[dashed,purple] (I) -- (K) -- (J);
\draw (A) node[below left] {A} -- (B) node[below right] {B} -- (C) node[above] {C} -- (D) node[above left] {D} -- (H) node[above] {H} -- (G) node[above right] {G} -- (F) node[right] {F} -- (B);
\draw (A) -- (D);
\draw (C) -- (G);
\draw[dashed] (A) -- (E) -- (H);
\draw[dashed] (E) node[above right] {E} -- (F);
%
\draw[dotted,gray] (B) -- (3,-2);
\draw[dotted,gray] (J) -- (3.5,-2);
\fill[red] (3,-1.5) circle (1.5pt) node[right] {L};
\coordinate (L) at (3,-1.5);
%
\draw[gray,dotted] (L) -- (K);
\coordinate (M) at (3.43,0.43);
\draw[red] (M) -- (K);
\end{tikzpicture}
\end{center}
\end{minipage}
\\
\begin{minipage}{\dimexpr\linewidth-5cm}
Les faces (BFGC) et (ADHE) sont parallèles et le plan (IJK) est sécant avec ces deux faces; de plus, I appartient aux deux plans donc l'intersection de (IJK) et (ADHE) est la droite parallèle à (KL) passant par I. On la trace donc et on trace en rouge la partie qui est sur la face (ADHE) :
\end{minipage}
&
\begin{minipage}{5cm}
\begin{center}
\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (3,0);
\coordinate (C) at (3,3);
\coordinate (D) at (0,3);
\coordinate (E) at (1,1);
\coordinate (F) at (4,1);
\coordinate (G) at (4,4);
\coordinate (H) at (1,4);
\coordinate (I) at (0,1.5);
\coordinate (J) at (1.5,0);
\coordinate (K) at (4,3);
\shade[left color=purple!5,right color=purple!40] (I) node[left] {I} -- (J) node[below] {J} -- (K) node[right] {K} -- cycle;
\draw[purple] (I) -- (J);
\draw[dashed,purple] (I) -- (K) -- (J);
\draw (A) node[below left] {A} -- (B) node[below right] {B} -- (C) node[above] {C} -- (D) node[above left] {D} -- (H) node[above right] {H} -- (G) node[above right] {G} -- (F) node[right] {F} -- (B);
\draw (A) -- (D);
\draw (C) -- (G);
\draw[dashed] (A) -- (E) -- (H);
\draw[dashed] (E) node[above right] {E} -- (F);
%
\draw[dotted,gray] (B) -- (3,-2);
\draw[dotted,gray] (J) -- (3.5,-2);
\fill[red] (3,-1.5) circle (1.5pt) node[right] {L};
\coordinate (L) at (3,-1.5);
%
\draw[gray,dotted] (L) -- (K);
\coordinate (M) at (3.43,0.43);
\draw[red] (M) -- (K);
%
\draw[dotted,gray] (I) -- (1,6) -- (H);
\draw[red,dashed] (I) -- (0.43,3.43);
\end{tikzpicture}
\end{center}
\end{minipage}
\end{tabular}

\newpage

\begin{tabular}{l@{~}|@{~}l}
\begin{minipage}{\dimexpr\linewidth-5cm}
De même, la section de la face (EFGH) par (IJK) est une droite parallèle à (IJ) passant par K :
\end{minipage}
&
\begin{minipage}{5cm}
\begin{center}
\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (3,0);
\coordinate (C) at (3,3);
\coordinate (D) at (0,3);
\coordinate (E) at (1,1);
\coordinate (F) at (4,1);
\coordinate (G) at (4,4);
\coordinate (H) at (1,4);
\coordinate (I) at (0,1.5);
\coordinate (J) at (1.5,0);
\coordinate (K) at (4,3);
\shade[left color=purple!5,right color=purple!40] (I) node[left] {I} -- (J) node[below] {J} -- (K) node[right] {K} -- cycle;
\draw[purple] (I) -- (J);
\draw[dashed,purple] (I) -- (K) -- (J);
\draw (A) node[below left] {A} -- (B) node[below right] {B} -- (C) node[above] {C} -- (D) node[above left] {D} -- (H) node[above right] {H} -- (G) node[above right] {G} -- (F) node[right] {F} -- (B);
\draw (A) -- (D);
\draw (C) -- (G);
\draw[dashed] (A) -- (E) -- (H);
\draw[dashed] (E) node[above right] {E} -- (F);
%
\draw[dotted,gray] (B) -- (3,-2);
\draw[dotted,gray] (J) -- (3.5,-2);
\fill[red] (3,-1.5) circle (1.5pt) node[right] {L};
\coordinate (L) at (3,-1.5);
%
\draw[gray,dotted] (L) -- (K);
\coordinate (M) at (3.43,0.43);
\draw[red] (M) -- (K);
%
\draw[dotted,gray] (I) -- (1,6) -- (H);
\draw[red,dashed] (I) -- (0.43,3.43);
%
\draw[red,dashed] (K) -- (3,4);
\end{tikzpicture}
\end{center}
\end{minipage}
\\
\begin{minipage}{\dimexpr\linewidth-5cm}
Il ne reste plus qu'à fermer la figure en rouge et nous obtenons la section du cube par le plan (IJK) :
\end{minipage}
&
\begin{minipage}{5cm}
\begin{center}
\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (3,0);
\coordinate (C) at (3,3);
\coordinate (D) at (0,3);
\coordinate (E) at (1,1);
\coordinate (F) at (4,1);
\coordinate (G) at (4,4);
\coordinate (H) at (1,4);
\coordinate (I) at (0,1.5);
\coordinate (J) at (1.5,0);
\coordinate (K) at (4,3);
\shade[left color=purple!5,right color=purple!40] (I) -- (J) -- (M) -- (K) -- (3,4) -- (0.43,3.43) -- cycle;
\draw[red,thick] (I) node[text=black,left] {I} -- (J) node[below,text=black] {J};
%\draw[dashed,purple] (I) -- (K) -- (J);
\draw (A) node[below left] {A} -- (B) node[below right] {B} -- (C) node[above] {C} -- (D) node[above left] {D} -- (H) node[above right] {H} -- (G) node[above right] {G} -- (F) node[right] {F} -- (B);
\draw (A) -- (D);
\draw (C) -- (G);
\draw[dashed] (A) -- (E) -- (H);
\draw[dashed] (E) node[above right] {E} -- (F);
%
\draw[dotted,gray] (B) -- (3,-2);
\draw[dotted,gray] (J) -- (3.5,-2);
\fill[red] (3,-1.5) circle (1.5pt) node[right] {L};
\coordinate (L) at (3,-1.5);
%
\draw[gray,dotted] (L) -- (K) node[right,text=black] {K};
\coordinate (M) at (3.43,0.43);
\draw[red,thick] (M) -- (K);
%
\draw[dotted,gray] (I) -- (1,6) -- (H);
\draw[red,dashed,thick] (I) -- (0.43,3.43);
%
\draw[red,dashed,thick] (K) -- (3,4);
%
\draw[red,thick,dashed] (J) -- (M);
\draw[red,thick] (0.43,3.43) -- (3,4);
\end{tikzpicture}
\end{center}
\end{minipage}
\end{tabular}