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WMA11/01 Oct 2019, Question 4: Area of a Triangle Using Sine

Pearson Edexcel International AS Level Mathematics · Pure Mathematics 1 (WMA11) · Calculator · 5 marks

The question, in short

For parallelogram ABCD with area 40 cm², sides AB = 10 cm and BC = 6 cm, and obtuse angle DAB, determine the obtuse angle and the diagonal BD.

Summarised in our own words. Use the official paper for the exact wording and any diagrams.

Part (a) · 3 marks

Work out the obtuse angle DAB in degrees, giving the result to 2 decimal places.

  1. 1Area = AB × AD × sin(DAB): 40 = 10 × 6 × sinθ
  2. 2sinθ = 2/3
  3. 3θ is obtuse: θ = 180° − 41.81° = 138.19°

Answer138.19°

Part (b) · 2 marks

Calculate the length of diagonal BD in cm, rounded to one decimal place.

  1. 1BD² = 10² + 6² − 2 × 10 × 6 × cos 138.19°
  2. 2BD² = 136 + 89.44 = 225.4…
  3. 3BD = 15.0 cm

AnswerBD = 15.0 cm

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Also searched as: WMA11 October 2019 · WMA11/01 · wma11 oct19 · IAS Maths Pure Mathematics 1 October 2019 · question 4.
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