A unit circle for derivation of the cosine difference formula using distance formular and Law of cosine

						JXG.Options.axis.ticks.majorHeight = -1;
JXG.Options.axis.ticks.insertTicks = false;
JXG.Options.axis.ticks.ticksDistance = -1;
var board = JXG.JSXGraph.initBoard('box1', {
    axis: true, boundingbox: [-1.3, 1.3, 1.3, -1.3], showcopyright: false,keepaspectratio: true, zoom: true,showNavigation: false, axis: false,
    });
	
var p1 = board.create('point', [0, 0],{name:'O',size: 1, label: {offset:[-15,-10], color:'blue'
}} );

c1 = board.create('circle',[p1, 1]);

p2 = board.create('glider',[0.89,0.45,c1],{size: 1,label:{ color:'blue'}});
p3 = board.create('glider',[-0.64,0.77,c1],{size: 1,label: {offset:[-15, 5], color:'blue'}});

var l1 = board.create('segment', [p1, p2]);
var l2 = board.create('segment', [p1, p3]);
var l3 = board.create('segment', [p2, p3]);
var l4 = board.create('axis', [[0.0, 0], [1, 0]]);
var l5 = board.create('axis', [[0.0, 0], [0, 1]]);
//var i = board.create('intersection', [c1, l4, 0]，{label:{color:'blue'}});
var i = board.create('point',[1,0],{size: 1,label: {offset:[5, 10], color:'blue'}});
a1 = board.create('angle',[i, p1, p3], {radius: 0.3});
a2 = board.create('angle',[i, p1, p2], {radius: 0.5});