男单 618

\begin{tikzpicture}
    \def\L{8}
    \coordinate (m) at (0.5*\L,0);
    \draw (m) node[below] {$m$};
    \draw[->] (0,0) -- (1.2*\L,0);
    \node [circle,draw] (i) at (0,0) [minimum size=3cm] {};
    \draw (i) node[below left] {$i$};
    \node [circle,draw] (j) at (\L,0) [minimum size=3cm] {};
    \draw (j) node[below right] {$j$};
    \coordinate (a) at (tangent cs:node=i,point={(m)},solution=1);
    \coordinate (c) at (tangent cs:node=i,point={(m)},solution=2);
    \coordinate (b) at (tangent cs:node=j,point={(m)},solution=1);
    \coordinate (d) at (tangent cs:node=j,point={(m)},solution=2);
    \draw (a) node[above] {$A$} -- (i.center)-- (c) node[below] {$C$} --
      (d) node[above] {$D$} -- (j.center)-- (b) node[below] {$B$} -- cycle;

    \draw[dashed] (0,0) -- (0,0.5*\L);
    \draw[dashed] (\L,0) -- (\L,0.5*\L);
    \node (l) at (0.5*\L,0.45*\L) {$l_{ij}$};
    \draw[< -] (0,0.45*\L) -- (l);
    \draw[->] (l) -- (\L,0.45*\L);
   
    \draw (m) +(0:8mm) arc (0:22:8mm);
    \path (m) +(8:1.2cm) node{$\alpha_{ij}$};
   
    \draw[dashed] (m) +($(0,0)-(a)$) -- (0,0);

    \draw[->] (0,0) +(0:18mm) arc (0:-22:18mm);
    \path (0,0) +(-8:22mm) node{$\alpha_{ij}$};

    \draw[->] (0,0) -- (3,-2) node[below right] {$\overrightarrow{v}_{ij}$};
    \draw[->] (0,0) +(0:8mm) arc (0:-32:8mm);
    \path (0,0) +(-18:12mm) node{$\beta_{ij}$};

    \draw[dashed] (m) +($(0,0)-(c)$) -- (0,0);
\end{tikzpicture}