Inequalities

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'});