Notice that cosine intersection with x axis has domain [-30, 30] by our param, otherwise it would be visible canvas domain. Zoom out and check. P.S. dg.Intersect(f1,f2) of type Function returns an array of Points.

dg.js example code

		var canvas = dg.Canvas("testcanvas", { border: "1px solid #ccc"});
		var axes = dg.Axes([canvas.width() / 4, canvas.height() / 1.5]).hide(false);
		
		var g = dg.Function(function(x) { return 1/x; });
		var f = dg.Function(function(x) { return x*x; }, "#ff0000").color(dg.color.rand());
		var f1 = dg.Function(function(x) { return Math.cos(x); }, dg.color.rand());
		
		var i1 = dg.Intersect(f, f1);
		
		var f2 = dg.Function(function(x) { return 0; });
		
		var i3 = dg.Intersect(f1, f2, [-30, 30]);