# Draggable exponential function

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Revision as of 10:41, 16 February 2016 by A WASSERMANN (talk | contribs)

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]

### The JavaScript code

```
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});
```

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