\PGset[0.8em]
\begin{picture}(16.5,9)

% 312x206
% 11x7
\drawline(1,1)(16.456,1)(12,8)(1,1) % ABCA

% -1/mAC = -1.571
\dashline[80]{0.2}(12,1)(12,8) % FC


\put( 0.7, 0.2 ){$\scriptstyle A$}
\put(15.8, 0.2 ){$\scriptstyle B$}
\put(11.7, 8.1 ){$\scriptstyle C$}
\put(11.7, 0.2 ){$\scriptstyle F$}


\end{picture}
\PGrestore