Question

Two circles intersect each other in points X
and Y. Secants through X and Y intersect
one of the circles in A and D and the other
in B and C respectively. A and B are on
opposite sides of line DC. Show that line
AD is parallel to line BC.​

Answer 1

Answer:

Two circles with centers X and Y intersect each other at A and B. The point A is joined with S, the midpoint of XY. The perpendicular to SA through A intersects the circles at P and Q. XS=YS and SA⊥PQ.