Chord of a Circle

A chord is a line segment
whose endpoints are on the circle.

If a line segment
starts from the center of the circle
(or passes through the center)
and is perpendicular to the chord,

then the line segment bisects the chord.

OP starts from the center of the circle.
And OP is perpendicular to the chord AB.

Then OP bisects AB.

So AP = PB.

OC is the radius.
OC = 5

OA is also the radius.
So OA = 5.

See △APO.
It's a right triangle.

The sides are (3, AP, 5).
So this right triangle is
a (3, 4, 5) right triangle.

Pythagorean Triple

So AP = 4.

AP = 4
AP = PB

So BP = 4

AP = BP = 4
AB = AP + PB

So AB = 4 + 4 = 8.

So 8 is the answer.