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JAMB Mathematics 1978 Question 29

Question 29

Trigonometry

A triangle has angles 30°, 15° and 135°. The side opposite to the angle 30°, has length 6cm. The side opposite to the angle 135° is equal to

  1. A.12cm
  2. B.6cm
  3. C.6√2cm
  4. D.12√2cm
  5. E.6√3cm.
Show the answer and explanation

Answer: C (6√2cm)

Explanation

By the sine rule, x/sin 135° = 6/sin 30°, so x = 12 × sin 45° = 12 × (√2/2) = 6√2cm.