Arrows are much more complicated that at first glance. If you use turtle style drawing to draw everything on the page, how to you render an arrowhead on a given line?

\begin{center}
\begin{pspicture}(0,-6)(6,0)
    

% y-axis
\rput(3.3,-0.5){ $\Im$ }
\psline{->}(3,-5.5)(3,-0.5)

% x-axis
\rput(5.5,-2.7){ $\Re$ }
\psline{->}(0.5,-3)(5.5,-3)

% quadrants
\rput(3.3,-0.8){ $\pi/2$ }
\rput(3.3,-5.5){ $\pi$ }
\rput(0.5,-2.7){ $3\pi/2$ }
\rput(5.2,-2.7){ $0$ }
	
		
% the circle
\pscircle(3,-3){ 2 }
	

 % new vector 
\rput(4.8,-1){$\mathbf{z}_0$}
\psline[linewidth=1.5 pt]{->}(4.73205124983367,-2.00000076602549)(5,-1)

 % new vector 
\rput(4.21421450055845,-1.58578737581288){$\mathbf{z}_1$}
\psline[linewidth=1.5 pt]{->}(4.73205124983367,-2.00000076602549)(4.41421450055845,-1.58578737581288)
\end{pspicture}
\end{center}

After much frustration, I found something promising, and note that the hope for this platform is to benefit people like this: \href{http://mathforum.org/library/drmath/view/54146.html}{mathforum.org}


Ironically, below is a snippet from the link above, where a person asked Dr. Math a question about arrows, and the responses were all in ASCII text! Imagine if Dr. Math had a mathematical diagramming system at his disposal!

\begin{verbatim} 

Hi, Johan.

Now that I've given you a chance to work this problem out, I want to 
let you know what I came up with, because I recognize it may be 
difficult for you to do on your own. It's an interesting problem.

We have a line segment from A(x0,y0) to B(x1,y1), and want to draw 
segments BC and BD of length d, at a t degree angle on either side of 
the segment at (x1,y1):

                                    B
                            d   ---o
                          ------ //
                     D o--   t /  /
                             /  t/ d
                           /    /
                         /      /
                       /       o
                     /         C
                   /
         slope m /
               /
             /
           /
         / s
       o - - - - - - -
      A

\end{verbatim}


The solution was this following formula:

\begin{nicebox}
\begin{align*}
 x &= x1 - \left[\left(x1-x0\right)cos(t) - \left(y1-y0\right)sin(t)\right]\frac{d}{l} \\     
 y &= y1 - \left[\left(y1-y0\right)cos(t) + \left(x1-x0\right)sin(t)\right]\frac{d}{l}
\end{align*}
\end{nicebox}

This enables us to use pslines and have arrows!

Here are four example lines with and without arrows:

\begin{center}
\begin{pspicture}(-3,-1)(3,4)
\psline{<->}(0,3)(1,3)
\psline{<-}(0,2)(1,2)
\psline{->}(0,1)(1,1)
\psline(0,0)(1,0)
\end{pspicture}
\end{center}

Which can be produced with the following \TeX:

\begin{verbatim}
\begin{pspicture}(-3,-3)(3,3)
\psline{<->}(0,3)(1,3)
\psline{<-}(0,2)(1,2)
\psline{->}(0,1)(1,1)
\psline(0,0)(1,0)
\end{pspicture}
\end{verbatim}
