In the given figure, ABCD is a cyclic quadrilateral, OB is the radius, PB is the tangent at point B, and ∠OBC=30°. AOC is a straight line passing through the centre O. Find the value of x.(2 marks)
In the given figrue,
∠OBP =90° and ∠OBC =30°
∠CBP =90°- 30°=60°
∠CAB =60°
(∠CAB = ∠CBP, alternate segment of chord))(1 mark)
In ∆OAB,
OA = OB
∠OAB = ∠OBA = 60°
So, ∠OAB + ∠OBA + ∠AOB =180°
(Sum of angles of a triangle is 180°)(1 mark)
60°+ 60°+ ∠AOB =180°
∠AOB =180°-120° = 60°