Angles in radian

i am kinda confused with this… i know in flash left top is 0,0 making flash stage as +ve quadrant. how do angles are measured in flash ( in rads i believe ??) …
i mean if you draw diagram showing directions as on maps, how many radians will be at position east ? west ? north ? south ??? …how do i say if mouse is clicked in northeast quadrant or NW or SE or SW quadrant ???