An inscribed trangle in a rectangle geometric shape

							var board = JXG.JSXGraph.initBoard('box1', {
        axis: true, boundingbox: [-15, 15, 15, -15], showcopyright: false,keepaspectratio: true,zoom: true,axis:false,showNavigation: false
    });

var p1 = board.create('point', [-12, -8],{name:'A', size: 1,face:"", fixed:true,color:'blue', label: {offset:[-15,0], color:'blue'}} );

var p2 = board.create('point', [-12, 8],{name:'B', size: 1,face:"", fixed:true,color:'blue', label: {offset:[-15,-5], color:'blue'}} );

var p3 = board.create('point', [10, 8],{name:'C', size: 1,face:"", fixed:true,color:'blue', label: {offset:[5,-5], color:'blue'}} );

var p4 = board.create('point', [10, -8],{name:'D', size: 1,face:"", fixed:true,color:'blue', label: {offset:[5,0], color:'blue'}} );

var l1 = board.create('segment', [p1, p2]);
var l2 = board.create('segment', [p2, p3]);
var l3 = board.create('segment', [p3, p4]);
var l4 = board.create('segment', [p4, p1]);


var g1 = board.create('glider', [-5, -1, l3],{name:'E', size: 1,face:"", fixed:true,color:'blue', label: {offset:[5,0], color:'blue'}});
var g2 = board.create('glider', [-4, -4, l4],{name:'F', size: 1,face:"", fixed:true,color:'blue', label: {offset:[-5,-10], color:'blue'}});

var l5 = board.create('segment', [p2, g1]);
var l6 = board.create('segment', [p2, g2]);
var l6 = board.create('segment', [g1, g2]);

var po1 =  board.create('polygon',[p1,p2,g2], {name:'x',withLabel:true, withLines: true, fillColor:'#46f',highlightFillColor:'#333',label: {offset:[-20,-10], color:'red'},	vertices:{face:'',label: { color:'blue'}} });

var po2 =  board.create('polygon',[p4,g1,g2], {name:'y',withLabel:true, withLines: true, fillColor:'#f6f',highlightFillColor:'#333',label: {offset:[10,-10], color:'red'},	vertices:{face:'',label: { color:'blue'}} });

var po3 =  board.create('polygon',[p2,g1,p3], {name:'z',withLabel:true, withLines: true, fillColor:'#eef',highlightFillColor:'#333',label: {offset:[40, 20], color:'red'},	vertices:{face:'',label: { color:'blue'}} });
var po4 =  board.create('polygon',[p2,g1,g2], {name:'w',withLabel:true, withLines: true, fillColor:'none',highlightFillColor:'#333',label: {offset:[-20, -10], color:'red'},	vertices:{face:'',label: { color:'blue'}} });