%\begin{center}
\begin{texdraw}
%\setunitscale 0.3

\drawdim in \linewd 0.003 \setunitscale 0.7
\arrowheadtype t:F
\arrowheadsize l:0.16 w:0.08

%begin textrectangle
\textref h:C v:C
\htext (0.79 -0.28){$s_1$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (1.29 -0.28){$a_1$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (1.80 -0.79){$a_2$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (1.29 -0.79){$s_2$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (2.31 -1.80){$s_{n-1}$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (2.83 -2.31){$s_{n}$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (2.83 -1.80){$a_{n-1}$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (1.81 -1.29){$\ddots$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (2.33 -1.29){$\ddots$}
%end textrectangle

%begin line
\move(0.54 -0.36)
\lvec(2.73 -2.55)
%end line

%begin line
\move(1.47 -0.02)
\lvec(3.08 -1.68)
%end line
\drawdim in \linewd 0.02

%begin line
\move(0.46 -0.02)
\lvec(0.46 -2.57)
%end line

%begin line
\move(3.16 -0.02)
\lvec(3.16 -2.57)
%end line

%begin line
\move(3.04 -0.02)
\lvec(3.16 -0.02)
%end line

%begin line
\move(3.04 -2.57)
\lvec(3.16 -2.57)
%end line

%begin line
\move(0.46 -2.57)
\lvec(0.58 -2.57)
%end line

%begin line
\move(0.46 -0.02)
\lvec(0.58 -0.02)
%end line
%begin textrectangle
\textref h:C v:C
\htext (2.56 -0.53){$\Large \boldsymbol{0}$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (1.03 -2.06){$\Large \boldsymbol{0}$}
%end textrectangle
%begin textrectangle
\textref h:C v:C
\htext (-0.66 -1.29){$Q^{(n-1)}AS^{(n-2)}=$}
%end textrectangle
\end{texdraw}
%\end{center}