# Riemann sum III

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Appromximate the integral of $\displaystyle{ f: R\to R, x\mapsto x^2 }$

Riemann sum type:

### The underlying JavaScript code

<form>Riemann sum type: <select id="sumtype" onChange="brd.update()">
<option value='left' selected> left
<option value='right'> right
<option value='middle'> middle
<option value='trapezoidal'> trapezoidal
<option value='simpson'> simpson
<option value='lower'> lower
<option value='upper'> upper
</select></form>

var brd = JXG.JSXGraph.initBoard('box', {axis:true, boundingbox:[-2,40,8,-5]});
var s = brd.create('slider',[[-1,30],[2,30],[3,50,500]],{name:'n',snapWidth:1});
var a = brd.create('slider',[[-1,20],[2,20],[-10,0,0]],{name:'start'});
var b = brd.create('slider',[[-1,10],[2,10],[0,6,10]],{name:'end'});
var f = function(x){ return x*x; };
var plot = brd.create('functiongraph',[f,function(){return a.Value();}, function(){return b.Value();}]);

var os = brd.create('riemannsum',[f,
function(){ return s.Value();}, function(){ return document.getElementById('sumtype').value;},
function(){return a.Value();},
function(){return b.Value();}
],
{fillColor:'#ffff00', fillOpacity:0.3});

brd.create('text',
[1,35,function(){ return 'Sum='+(JXG.Math.Numerics.riemannsum(f,s.Value(),document.getElementById('sumtype').value,a.Value(),b.Value())).toFixed(4); }]);