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. Then, find the value of x.
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Solution
In the given figrue, ∠OBP=90∘
and ∠OBC=30∘
∴∠CBP=90∘−30∘=60∘⇒∠CAB=60∘ [∵∠CAB=∠CBP, alternate segment of chord]
In ΔOAB,
OA =OB ⇒∠OAB=∠OBA=60∘
In ΔOAB, ∠OAB+∠OBA+∠AOB=180∘⇒60∘+60∘+∠AOB=180∘∴∠AOB=180∘−120∘=60∘