var angle = 0;
var amplitude = 50;
var y = Stage.height/2;
var x = 0;

moveTo(0,Stage.height/2);
lineStyle(2,0xFF0000,100);

onEnterFrame = function (){
y = Stage.height/2 + amplitude*Math.sin((angle*Math.PI)/180);
x += 1;
angle += 5;
lineTo(x,y);
}