CurveTo problem

Hi guys ! This is my problem! I want to create a pie chart… . I used
_root.a=Math.cos(0*Math.PI/180)radius;
_root.b=Math.sin(0
Math.PI/180)radius;
for my first point
and
_root.c=Math.cos(degrees
Math.PI/180)radius;
_root.d=Math.sin(degrees
Math.PI/180)*radius;
for the second point.
so my problem is that i cant calculate the control points to join the 2 points?
anybody knoes ???