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    • Question

      AB is the diameter of a circle centered at O. A tangent

      drawn at point C intersects the extension of AB at point D. If ∠CAB = 38°, find the value of ∠CDB.
      A 128° Correct Answer Incorrect Answer
      B 112° Correct Answer Incorrect Answer
      C 102° Correct Answer Incorrect Answer
      D 132° Correct Answer Incorrect Answer

      Solution

      ATQ,

      Image

      Angle made by the diameter of a circle on the arc of the circle is 90°, i.e. ∠ACB = 90°.

      Sum of all angles in a triangle is 180°.

      So, ∠CAB + ∠CBA + ∠ACB = 180°

      Or, 38° + ∠CBA + 90° = 180°

      Or, ∠CBA = 180° - 128°

      Or, ∠CBA = 52°

      Now, ∠CBA + ∠CDB = 180°

      (Linear pair of angles)

      So, ∠CDB = 180 - 52 = 128°

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