how to draw angle line? [duplicate]

Question

Possible Duplicate:
how to draw special line in a picture

I use the code below to draw a picture, however the line is straight from s2 to s4 refer to the image.

However, I want the line like an angle like the red line in the picture.would someone help me how to do it?

\usepackage{tikz}
\usetikzlibrary{trees}
\resizebox{.5\textwidth}{!}{
\tikzset{level 1/.style={level distance=0.7cm, sibling distance=3cm}}
\tikzset{level 2/.style={level distance=0.7cm, sibling distance=6cm}}

\tikzset{bag/.style={text centered,yshift=-0.2cm}}
\begin{tikzpicture}[grow=down, -stealth]
\node[bag]{$S_0{:}(B,true,0)$}
    child{ edge from parent node[right]{$\lsInvoke \_ DS$}; \node[bag]{$S_1{:}(R_{good})$}
            child{ edge from parent node[right]{and}; \node[bag]{$S_2{:}(and)$}
                    child[missing]
                    child{ edge from parent node[right=0.1cm]{$[else]$}; \node[bag]{$S_3{:}(A_1)$}
                    }
                    child{ edge from parent node[right=0.9cm]{$[if]$}; \node[bag]{$S_4{:}(R_{good})$}
                    }
            }
    };
\end{tikzpicture}} 

Answer 1

i can't compile your code, and don't have any experience with trees, which appears to draw the path for you. this should demonstrate the concept i think you're looking for though:

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
    \coordinate (A) at (0,0);
    \coordinate (B) at (5,-1);
    \draw (A) -- (B);
    \draw[thick,dashed,red,->] (A) -| (B);
\end{tikzpicture}
\end{document}

which produces:

the most important part for you here is the use of -| instead of -- to create the path in a rectilinear coordinate system instead of the standard one. when used with draw, instead of drawing a straight line, this draws the components of that line.

perhaps you can just create named coordinates at S_2 and S_4 and overlay the rectilinear path over it?