\PGset[0.8em]
\begin{picture}(17,12)

% 436x290
% 15(5.5)x10
\drawline(1,11)(6.5,1)(16,1)(1,11) % ACBA

\dashline[80]{0.2}(1,11)(1,1)(6.5,1) % ADC


\put(0.7,11.1 ){$\scriptstyle A$}
\put(6.2, 0.2 ){$\scriptstyle C$}
\put(16.1, 0.8 ){$\scriptstyle B$}
\put(0.7, 0.2 ){$\scriptstyle D$}


\end{picture}
\PGrestore