Help with Math.atan2(); Rotating Movieclip to point at mouse

[LEFT]I am trying to make a line point to wherever the cursor is when i stumbled upon the Math.atan2(); function. It appeared that i would put line.rotation = Math.atan2(1,1); to get 45 degrees or pi/4, but i was wrong. It barely moved the movieclip at all.

So what i’m trying to do is to get this movie clip to rotate along with the mouse so the line is always pointing at the cursor.

Also, how would you get movieclip to move along the line created by the line of these two points?

Thanks in advance!
[/LEFT]