Prove that a diameter AB of a circle bisects all those chords parallel to the tangent at point A.
According to question
Let us take a chord EF || XY
Here
( tangent at any point of the circle is perpendicular to the radius through the point of contact)
(Corresponding angles)
Thus AB bisects EF
Hence AB bisects all the chords parallel to the tangent at point A.
Hence Proved