Two circles intersect at two points A and B. If AD and AC are diameters of the circles, then which of the following steps is INCORRECT in order to prove that B lies on the line segment DC?
(P) Join AB.
(Q) ∠ABD = 90° and ∠ABC = 90° (Angle in semicircle)
(R) ∠ABD + ∠ABC = 360°
(S) DBC is a straight line segment. Hence B lies on the line segment DC.
AP
BQ
CR
DS