Math Question

Can someone explain to me how to graph sine and cosine without the cartesian plots? I understand y+ goes down and x+ goes right for graphics. So I think what I am wondering is there a way to move the origin of the graph say to the middle of the screen. Also maybe set the coordinates back to the cartesian way. And maybe an equation that converts pixels to points? pi apprx = 3.14 but if i draw a line 3.14 then it goes no where bc its using pixels. Thanks for any help.

If you make a movie clip on top of the stage, with the same dimensions of the stage (say its the default, 550 x 400), you can get the width and height of the movie clip and divide by 2.

xOrigin = myMovieClip_mc._width/2;
yOrigin = myMovieClip_mc._height/2;

Now do your coordinates from these points.