In the figure; P and Q are the points of intersection of two circles with centres O & O'. If straight line APB and CQD are parallel to OO', then what is the ratio of OO' and AB?
1:2
Draw OM⊥AP & O′N⊥PB.
Now quadrilateral OO'NM is a rectangle, since all of its angles are 90∘
OO' = MN
We know perpendicular from the Centre of the circle to the chord bisects the chord, therefore:
AM=MP=12AP
PN=NB=12BP
OO′=MN
=PM+PN
=AP2+BP2
=(AP+BP)2
=AB2
∴OO′:AB=1:2