A triangle PQR is inscribed in a circle with its centre at O. A tangent PT is drawn at P such that \angle QPT = 36^\circ. What is \angle POQ equal to ?

  1. A. 36^\circ
  2. B. 54^\circ
  3. C. 72^\circ
  4. D. 108^\circ

Correct Answer: C. 72^\circ

Explanation

By the Alternate Segment Theorem, the angle between the tangent and chord PQ equals the angle in the alternate segment, so \angle PRQ = 36^\circ. The angle subtended at the centre is twice the angle at the circumference, so \angle POQ = 2 \times 36^\circ = 72^\circ.

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