A trangle geometric shape

						var board = JXG.JSXGraph.initBoard('box1', {
boundingbox: [-2, 10, 10, -3],showcopyright: false,showNavigation: false,axis: true,defaultAxes: {
    y: { ticks: {majorHeight: 5 } },
	x: { ticks: {majorHeight: 5 } },
  }, 
});

var p1 = board.create('point', [1, 1],{name:'(1,1)',size:1, fixed: true, label:{offset:[-10,-13]}});
var p2 = board.create('point', [3, 1],{name:'(3,1)',size:1,fixed: true,label:{offset:[-10,-13]}});
var p3 = board.create('point', [5, 7],{name:'(5,7)',size:1 ,fixed: true,label:{offset:[10,0]}});
var l1 = board.create('segment', [p1, p2]);
var l2 = board.create('segment', [p1,p3],);
var l3 = board.create('segment', [p2,p3],);
var pp1 = board.create('perpendicularpoint', [p3, l1],{name:'',face:''});
var l4 = board.create('segment', [p2,pp1],{dash:2});
var l5 = board.create('segment', [p3,pp1],{dash:2});
var a1 = board.create('angle', [p3, pp1, p2],{name:' '});