title: Latex / Tikz: draw a vertical line to a straight line
body: <p>Maybe you can help me, I try to draw a line from a Point/Coordinate to a straight line. I use Tikz to draw.</p>
  
  <pre><code>      \begin{tikzpicture}
        \coordinate [label=left:$A$] (A) at (-5,-5){};
        \coordinate [label=right:$B$] (B) at (5,-5) {};
        \coordinate [label=right:$C$] (C) at (5,1) {};
        \coordinate [label=left:$D$] (D) at (-5,1) {};
  
        \draw [thick] (A) -- node[midway] {$\parallel$} (B) -- node[sloped]{$\parallel$} (C) -- (D) -- cycle;
  
        \coordinate (S1) at ($(D)!0.66!(C)$);
        \coordinate (S2) at ($(A)!0.11!(B)$);
        \draw [very thick] (S1) -- node[above]{x} (S2);
        \draw [red!100, thick] (S1) -- node[above]{T} (A -| B );
        \end{tikzpicture}
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/ej1Aa.png" rel="nofollow noreferrer">This where the red line should go</a></p>
  
  <p>the red line should go from coordinate (S1) to the straight line (A -- B) vertically.
  I tried it to draw it like this:</p>
  
  <pre><code>     \draw [red!100, thick] (S1) -- node[above]{T} (A -| B );
  </code></pre>
  
  <p>But then he draw a line to coordinate A</p>
  
  <p>Thank you,</p>