Angle

The underlying JavaScript code

var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-2,2,2,-2]});
var A = brd.create('point', [-1,-1]),
    B = brd.create('point', [1,-1]),
    C = brd.create('point', [0,1]),
    alpha = brd.create('angle', [B,A,C], {type:'sector', orthoType:'square, orthoSensitivity:2, radius:0.5});