Given BD bisects ∠ABC, ∠A+∠C=180° $. Prove AD=DC

						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', [-5, 4],{name:'A', size: 1,face:"", color:'blue', fixed: true,label: {offset:[-25,10], color:'blue'}} );
var p2 = board.create('point', [-10, -4],{name:'B', size: 1,face:"", color:'blue', fixed: true,label: {offset:[-15,-10], color:'blue'}} );

var p3 = board.create('point', [2, -4],{name:'C', size: 1,face:"", color:'blue', fixed: true,label: {offset:[5,-10], color:'blue'}} );
var l1 = board.create('segment', [p1, p2]);
var l2 = board.create('segment', [p2, p3]);

var bi1 = board.create('bisector', [p1, p2, p3],{visible:false});
var  a = board.create('slider',[[-4,-12],[4,-12],[3,12.24,26]], {name:'a'});

var g1 = board.create('glider', [0.7,1.95,bi1],);

var l3 = board.create('segment', [p1, g1]);
var l4 = board.create('segment', [p3, g1]);

board.create('text',[-8,14, function(){ return "AD = "+ l3.L().toFixed(2);}]);

board.create('text',[-1,14, function(){ return "CD = "+ l4.L().toFixed(2);}]);
					

Triangle posted 1 year ago

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