View source for Draggable exponential function

Plot the function
:<math> y = e^{ax}</math>
where the parameter <math>a</math> is determined by the Point <math>A=(x_A, y_A)</math>.

That means, 
:<math> a = log(y_A) / x_A </math>

<jsxgraph width="400" height="400" box="box1">
var board = JXG.JSXGraph.initBoard('box1', {boundingbox: [-5, 20, 5, -2], axis:true});

var A = board.create('point', [1, Math.exp(1)]);
var graph = board.create('functiongraph', [
         function(x) {
            var a = Math.log(A.Y()) / A.X();
            return Math.exp(a * x);
         }]);
           
var txt = board.create('text', [-3, 10, function () {
           return "a = " + (Math.log(A.Y()) / A.X()).toFixed(2);
          }], {fontSize: 16});
</jsxgraph>
<html>
<input type="button" onClick="alert('a = ' + (Math.log(A.Y()) / A.X()).toFixed(2))" value="Show value of a" />
</html>

===The JavaScript code===
<source lang="javascript">
var board = JXG.JSXGraph.initBoard('box1', {boundingbox: [-5, 20, 5, -2], axis:true});

var A = board.create('point', [1, Math.exp(1)]);
var graph = board.create('functiongraph', [
         function(x) {
            var a = Math.log(A.Y()) / A.X();
            return Math.exp(a * x);
         }]);
           
var txt = board.create('text', [-3, 10, function () {
           return "a = " + (Math.log(A.Y()) / A.X()).toFixed(2);
          }], {fontSize: 16});
</source>

<source lang="html4strict">
<input type="button" onClick="alert('a = ' + (Math.log(A.Y()) / A.X()).toFixed(2))" value="Show value of a" />
</source>

[[Category:Examples]]
[[Category:Calculus]]