Solution to the above question:
As the red circles move about segment 
, they cover the area we are looking for. On the left side, the circle must move around pivoted on 
. On the right side, the circle must move pivoted on 
However, at the top and bottom, the circle must lie on both A and B, giving us our upper and lower bounds.
This egg-like shape is 
.
The area of the region can be found by dividing it into several sectors, namely
