Harmonic Waves

    board1 = JXG.JSXGraph.initBoard('jxgbox1', {originX: 300, originY: 200, unitX: 50, unitY: 50});
    board1.suspendUpdate();
    board1.createElement('axis', [[0,0], [1,0]], {});
    board1.createElement('axis', [[0,0], [0,1]], {});
    var s = board1.createElement('slider', [[0.75,-2],[5,-2],[0,0,10]], {name:'S'});
    board1.createElement('functiongraph', [
        function(t) {
            var val = 0;
            var k = 1;
            for(var i = 0; i < Math.floor(s.X()) + 1; i++) {
                val = val + Math.sin(2*Math.PI*k*t)/k;
                k += 1;
            }
            return val+2;
            }, -10, 10], {strokeColor: "#bb0000"});
    
        board1.createElement('functiongraph', [
            function(t) {
                var val = 0;
                var k = 1;
                for(var i = 0; i < Math.floor(s.X()) + 1; i++) {
                    val = val + Math.sin(2*Math.PI*(2*k-1)*t)/(2*k-1);
                    k += 1;
                }
                return val-2;
                }, -10, 10], {strokeColor: "#cc5520"});

    board1.unsuspendUpdate();