An Algebra solution is getting very messy so I tried it with some actual numbers:
The circle = the unit circle: y = √1x²
A=(1,0)
B=(1,0)
C=(4/5,3/5)
D=(5/13,12/13)
Gives
P=(0,9/11)
E=(1/3,4/9)
F=(1/3,0)
Setting Q perpendicular gives
Q=(101/195,44/65)
With a little vector work ∠PAQ and ∠PBQ both come out to
arccos(11√(1170)/390) ≈ 15.255º
I'll try again with C=(xc,yc) and D=(xd,yd) soon if I get a chance.

Posted by Jer
on 20131210 16:19:51 