A chord of a circle is equal to its radius. A tangent is drawn to the circle at an extremity of the chord. The angle between the tangent and the chord is
OA = OB (radii of circle)
OA = OB = AB (radii and chord are equal)
$$\therefore$$ $$\triangle$$ AOB is an equilateral triangle.
=> $$\angle$$ AOB = $$\angle$$Â OAB = $$\angle$$Â OBA = $$60^\circ$$
Also, $$\angle$$ OBD = $$90^\circ$$
=>Â $$\angle$$Â OBA +Â $$\angle$$Â ABD = $$90^\circ$$
=>Â $$\angle$$Â ABD = $$90^\circ-60^\circ=30^\circ$$
=> Ans - (A)
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