# Inequalities

From JSXGraph Wiki

Revision as of 14:11, 2 June 2017 by A WASSERMANN (talk | contribs)

To graph inequalities of the form
*y <= b/a * x + c/a*
a line of the form

```
line = b.create('line', [c, b, a]);
ineq = b.create('inequality', [line]),
```

and an equality of this line have to be created.
If one wants to show "greater than", *inverse:true* has to be used:

```
line = b.create('line', [c, b, a]);
ineq = b.create('inequality', [line], {inverse:true}),
```

In the following example, two lines are shown.
The first, black line has the equation *y = c* or *0 = -1y + 0x + c*,
the second, blue line has the equation *y = 2/3 x + 1* or *0 = -3y + 2x +1*.

In case *a = 0*, that is if the equation of the line is *bx + c = 0*, the area of the inequality
*bx + c <= 0* is shown.

### The JavaScript code

```
var b = JXG.JSXGraph.initBoard('box1', {boundingbox: [-5, 5, 5, -5], axis:true});
var c = b.create('slider', [[-3,4], [2,4], [-5,1,5]]),
line1 = b.create('line', [function() { return [c.Value(), 0, -1]; }], {strokeColor: 'black'}),
ineq1 = b.create('inequality', [line1], {inverse: true}),
line2 = b.create('line', [1, 2, -3]), // Line y = 2/3 x + 1 or 0 = -3y + 2x +1
ineq2 = b.create('inequality', [line2], {fillColor: 'yellow'});
```