A unit circle for derivation of the cosine difference formula using Law of Cosine and Pythagorean Theorem

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

p2 = board.create('point',[0.89,0.45],{size: 1,fixed:true, label:{ color:'blue'}});
p3 = board.create('point',[-0.64,0.77],{size: 1,fixed:true, label: {offset:[-15, 5], color:'blue'}});
c1 = board.create('circle',[p1, p2]);

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 pp1 = board.create('perpendicularpoint', [p3, l4],{size: 1,label: {offset:[-15,-10], color:'blue'}});
var l6 = board.create('segment', [p3, pp1]);
var pp2 = board.create('perpendicularpoint', [p3, l5],{size: 1,label: {offset:[10,0], color:'blue'}});
var l7 = board.create('segment', [p3, pp2]);
var pp3 = board.create('perpendicularpoint', [p2, l5],{size: 1,label: {offset:[-15,-8], color:'blue'}});
var l8 = board.create('segment', [p2, pp3]);
var pp4 = board.create('perpendicularpoint', [p2, l4],{size: 1,label: {offset:[0,-10], color:'blue'}});

var l9 = board.create('segment', [p2, pp4]);
a1 = board.create('angle',[pp4, p1, p3], {radius: 0.3});


a2 = board.create('angle',[pp4, p1, p2], {radius: 0.5});

var pp5 = board.create('perpendicularpoint', [pp3, l6],{size: 1,label: {offset:[-15,-8], color:'blue'}});

var perp1 = board.create('perpendicularsegment', [l6, pp3] ,{dash:2});