Arsir daerah busur

\begin{tikzpicture}
\path (0,0) coordinate (O) (3.5,0) coordinate (A) (3.5,3.5) coordinate (B) (0,3.5) coordinate (C) (0,1.75) coordinate (D) (3.5,1.75) coordinate (E);
\draw[bistre,thick,pattern=north west lines,pattern color=bistreb] (E)--(B) arc(0:180:1.75cm)--(D) arc(90:0:1.75cm) arc(180:90:1.75cm)--cycle;
\draw[bistre,thick] (D)--(O)--(A)--(E);
\draw[|{Stealth}-{Stealth}|,rusia] (3.7,1.75)--(3.7,3.5) node[midway,right]{7 cm};
\draw[|{Stealth}-{Stealth}|,rusia] (0,-.2)--(3.5,-.2) node[midway,below]{14 cm};
\end{tikzpicture}