Connections between Mapping Diagrams and Graphs.
    
    In the left window is coordinate plane with a point $P = (-2,4)$ .
    In the right window  is a mapping diagram  with an arrow,
    $<a,b>$, between the point $a=2$ on the left axis and the
    point $b=3$ on the right axis.
    
    To see the arrow on the mapping diagram that corresponds to the
      point P: Check the box in the left window  "Show/Hide
    ..." .
    In the mapping diagram will appear an arrow,
    $<p_1,p_2>$,  between points $p_1=-2$ and $p_2=4$
    corresponding to the point $P$. You can move the point $P$ freely in
    the plane with your mouse and see the corresponding mapping diagram
    change. 
    Removing the check in  the box will hide the arrow and points
    in the mapping diagram.
    
    To see the point and arrows in the coordinate plane that
      corresponds to the mapping diagram arrow between the points $A$
      and $B$: Check the boxes in the right window  "Show/Hide
    Point on Graph on Graph"  and "Show/Hide Arrows on Graph".
    In the coordinate plane will appear the point with coordinates
    $(a,b) = (2,3)$. The second box will show arrows, one from the point
    labelled $a_1 = 2$ on the $X$- axis to the point  $(2,3)$ and
    another from the point $(2,3)$ to the point labelled $b_1 = 3$ on
    the $Y$-axis  corresponding to the mapping diagram arrow
    $<a,b>$ between the points $a$ and $b$.
    You can move the points $a$ and $b$ freely in the mapping diagram
    with your mouse and see the corresponding points and arrows change.
    
    Removing the checks in these boxes will hide the arrows and points
    in the coordinate plane.