A triangle with inscribed circle for proving r=4Rsin(A/2)sin(B/2)sin(C/2)

						var board = JXG.JSXGraph.initBoard('box1', {
boundingbox: [-8, 11, 8, -7],showNavigation:false, showcopyright: false, axis: false,
});
var p2 = board.create('point', [1.5, 7.5],{face:'',});
var p1 = board.create('point', [-7, 0],{face:'',label:{offset:[-12,10]}});

var p3 = board.create('point', [6, 0],{face:''});
var l1 = board.create('segment', [p1, p2],{withlabel:true,name:'c',label:{offset:[-10,10]}});
var l2 = board.create('segment', [p2,p3],{withlabel:true,name:'b',label:{offset:[10,0]}});
var l3 = board.create('segment', [p1, p3],{withlabel:true,name:'a',label:{offset:[0,-10]}});

var ic1 = board.create('incircle', [p1, p2, p3]);
var ice1 = board.create('incenter', [p1, p2, p3],{face:'',name:''});
var perp1 = board.create('perpendicularsegment', [l1, ice1],{withlabel:true,name:'r',color:'blue',label:{offset:[-10,20]}});
var perp2 = board.create('perpendicularsegment', [l2, ice1],{withlabel:true,name:'r',color:'blue',label:{offset:[-20,-20]}});
var perp3 = board.create('perpendicularsegment', [l3, ice1],{withlabel:true,name:'r',color:'blue',label:{offset:[-10,-20]}});
var l4 = board.create('segment', [p1, ice1]);
var l5 = board.create('segment', [p2, ice1]);
var l6 = board.create('segment', [p3, ice1]);
var i1 = board.create('intersection', [perp3, l3],{face:'',label:{offset:[10,-10]}});