# Polygon II

From JSXGraph Wiki

The triangle *ABC* can be moved by dragging *A* and it can be rotated around *A* by moving *B*.

### The underlying JavvaScript code

For the elements *c1*, *p3*, *line* the attribute *visible* should be set to false.

```
var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-3,3,3,-3]});
var p1 = brd.create('point',[-1,-1]);
var c1 = brd.create('circle',[p1,3],{strokeOpacity:0.1}); //
var p2 = brd.create('glider',[2,-1,c1]); // p2 glides on circle c1
var rot = brd.create('transform',[function(){ return Math.PI/4;},p1],{type:'rotate'}); // rot is defined by the angle BAC
var p3 = brd.create('point',[p2,rot],{fixed:true,size:1,name:'h1'}); // h1: B rotated around A with angle rot
var line = brd.create('line',[p1,p3],{strokeOpacity:0.1}); // line through A and h1
var p4 = brd.create('glider',[0,0.5,line],{fixed:true}); // C is on the line with a fixed distance from A
var poly = brd.create('polygon',[p1,p2,p4], {fillOpacity:0.05});
```