Find the distance from DD to plane BEC

						var board = JXG.JSXGraph.initBoard('box1', {
axis: true, boundingbox: [-15, 15, 15, -15], showcopyright: false,keepaspectratio: true, axis: false, zoom: false,showNavigation: false
  });
  
var p1 = board.create('point', [-11, -12],{name:'A', size: 1,face:"",fixed: true,  label: {offset:[-5,-10], }} );
var p2 = board.create('point', [-3, -12],{name:'B', size: 1,face:"",  fixed: true,label: {offset:[-5,-10], }} );

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

var p4 = board.create('point', [-6, -8],{name:'D', size: 1,face:"",  fixed: true,label: {offset:[5,10], }} );
var l1 = board.create('segment', [p1, p2],{strokeWidth:2});
var l2 = board.create('segment', [p2,p3],{strokeWidth:2});
var l3 = board.create('segment', [p3,p4],{strokeWidth:2,dash: 2});
var l4 = board.create('segment', [p4,p1],{strokeWidth:2,dash: 2});
var p5 = board.create('point', [-6, -1],{name:'E', size: 1,face:"", fixed: true,label: {offset:[-20,0],}} );

var l5 = board.create('segment', [p4,p5],{strokeWidth:2,dash: 2});
var l6 = board.create('parallel', [p5,l4],{visible:false});
var l7 = board.create('parallel', [p1,l5],{visible:false});
var i1 = board.create('intersection', [l6,l7],{name:"F",size: 1,face:"",label: {offset:[-20,0], }});
var l8 = board.create('segment', [p5,i1],{strokeWidth:2});
var l9 = board.create('segment', [i1,p1],{strokeWidth:2});
var l10 = board.create('segment', [i1,p2],{strokeWidth:2});
var l11 = board.create('segment', [p5,p2],{strokeWidth:2});
var l12 = board.create('segment', [p5,p3],{strokeWidth:2});
var mp1 =  board.create('midpoint', [p5,p4],{name:'M', size: 1,face:"",  label: {offset:[-15,0], }} );
var lmc =  board.create('parallel', [l12, mp1],{visible:false});
var imcd =   board.create('intersection', [l3, lmc],{face:''});
var l13 = board.create('segment', [p1,mp1],{strokeWidth:2,dash: 2});
var pp1 = board.create('perpendicularpoint', [p4, l11],{face:''});
var l14 = board.create('segment', [p4,pp1],{strokeWidth:2,dash: 2});