Two tangents at the extremities of the diameter of a circle

						var board = JXG.JSXGraph.initBoard('box1', {
boundingbox: [-10, 10, 10, -10],showNavigation:false, showcopyright: false, axis: false,
});

var p1 = board.create('point', [-0.5, 2.0],{name:'O',face:'',label:{offset:[-20,0]}});
var c1 = board.create('circle', [p1, 4],);
var g1 = board.create('glider', [-0.5, 6, c1]);
var l1 = board.create('line', [p1,g1],{visible:false});
var i1 = board.create('intersection', [l1, c1,1],);
var perp1 = board.create('perpendicular', [l1, g1],{color:'blue'});
var perp2 = board.create('perpendicular', [l1, i1],{color:'blue'});