--- loncom/homework/templates/functionplottwo.problem	2010/11/13 03:23:03	1.2
+++ loncom/homework/templates/functionplottwo.problem	2010/11/24 02:53:18	1.4
@@ -3,26 +3,32 @@
 <startouttext />
 Make a sketch of the electrostatic potential (zero at infinity) of a negative point charge located at x=$x m.
 <endouttext />
-<functionplotresponse xaxisvisible="yes" xlabel="x [m]" gridvisible="yes" ylabel="V(x) [V]" id="11" xmax="30" yaxisvisible="yes" xmin="-4" ymin="-10" ymax="10">
+<functionplotresponse xaxisvisible="yes" xlabel="x [m]" gridvisible="yes" ylabel="V(x) [V]" id="11" xmax="30" yaxisvisible="yes" xmin="-4" ymin="-10" ymax="10" answerdisplay="-4/abs(x-$x)">
 <functionplotelements>
 <spline initx="-2" inity="0" index="A" order="2" scalex="4" />
 <spline index="B" order="2" initx="12" inity="0" scalex="4" />
 </functionplotelements>
 <functionplotruleset>
 <functionplotrule relationship="eq" value="undef" derivative="0" xinitial="$x" index="chargeposition" derivativeorder="0" />
-<functionplotrule relationship="lt" value="0" derivativeorder="0" xinitiallabel="start" xfinallabel="chargeleft" />
+<functionplotrule relationship="lt" value="0" derivativeorder="0" xinitiallabel="start" xfinallabel="chargeleft" index="negleft" />
 <functionplotrule relationship="lt" value="0" derivativeorder="1" xinitiallabel="start" xfinallabel="chargeleft" />
-<functionplotrule relationship="le" value="0" derivativeorder="2" xinitiallabel="start" xfinallabel="chargeleft" />
+<functionplotrule relationship="le" value="0" derivativeorder="2" xinitiallabel="start" xfinallabel="chargeleft" percentageerror="20" />
 <functionplotrule relationship="eq" xinitiallabel="chargeleft" xfinallabel="chargeright" value="undef" derivativeorder="0" />
-<functionplotrule relationship="lt" value="0" derivativeorder="0" xinitiallabel="chargeright" xfinallabel="end" />
+<functionplotrule relationship="lt" value="0" derivativeorder="0" xinitiallabel="chargeright" xfinallabel="end" index="negright" />
 <functionplotrule relationship="gt" value="0" derivativeorder="1" xinitiallabel="chargeright" xfinallabel="end" />
-<functionplotrule relationship="le" value="0" derivativeorder="2" xinitiallabel="chargeright" xfinallabel="end" />
+<functionplotrule relationship="le" value="0" derivativeorder="2" xinitiallabel="chargeright" xfinallabel="end" percentageerror="20" />
 </functionplotruleset>
 
 <hintgroup showoncorrect="no">
 <hintpart on="chargeposition">
 <startouttext />The charge is not in the correct position.<endouttext />
 </hintpart>
+<hintpart on="negleft">
+<startouttext />The potential is zero at negative infinity, and the charge is negative.<endouttext />
+</hintpart>
+<hintpart on="negright">
+<startouttext />The potential is zero at positive infinity, and the charge is negative.<endouttext />
+</hintpart>
 </hintgroup>
 </functionplotresponse>
 </problem>