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}),
    beta = brd.create('angle', [C,B,A], {type:'sector', orthoType:'sectordot', orthoSensitivity:2, radius:0.2});