uh,
where abouts is your pivot point for a pie piece?
from the picture i assume you want all 7 pieces on the same plane touching each other at the sharpest end of the triangle?

maybe you need to relocate the pivot point. if you hit 'ins' on your keyboard then yo ucan move the pivot point around.
if you hold down 'v' and dragon along one of the lines sticking out from the pivot point then you can move it in that direction
then you can just move the pivot point to the sharp angle on your pie piece and then hit duplicate special.

if you need to get the pivot point back to the center of the object just hit modify->center pivot point