Inverse mapping of the power function

<link rel="stylesheet" type="text/css" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css" />
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/prototype.js"></script>
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<div id="jxgbox" class="jxgbox" style="width:600px; height:400px;"></div>

b = JXG.JSXGraph.initBoard('jxgbox', {originX: 220, originY: 300, unitX: 40, unitY: 40});
b.suspendUpdate();
b.createElement('axis', [[0,0], [1,0]], {});
b.createElement('axis', [[0,0], [0,1]], {});
var n = b.createElement('slider',[[-5,-1],[5,-1],[-5,1,5]],{name:'n'});
b.createElement('functiongraph', [function(t){ return t}],{strokeColor:'#000000',dash:1,strokeWidth:1});
b.createElement('functiongraph', [function(t){ return b.pow(t,n.Value()); },0.001,8],{strokeColor:'#ff0000'});
b.createElement('functiongraph', [function(t){ return b.pow(t,1/n.Value()); },0.001,8],{strokeColor:'#ff0000',dash:2});
b.unsuspendUpdate();