2025 · Standard · Set 4 · Part 1·Q24·2 marks

Introduction to Trigonometry

Question

Prove that the tangents drawn at the ends of a diameter of a circle are parallel.

Approach

Let AB be diameter. Tangents at A and B are perpendicular to AB (tangent perpendicular to radius). So both make 90° with AB, hence they are parallel by alternate interior angles being equal.

Step-by-step working

  1. 1

    Draw correct figure with diameter and tangents

    0.5 marks
  2. 2

    Show

    0.5 marks
  3. 3

    Conclude co-interior angles sum to 180°, so tangents are parallel

    1 mark

Concepts used

tangentdiameterparallel lines

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