4MA1/1F Jan 2021, Question 26: Using Trigonometry and Pythagoras Together
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 1F (Foundation) · Calculator · 4 marks
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The question, in short
Isosceles triangle ABC has D the midpoint of AC, DB = 16 cm perpendicular to AC, and angle DAB = 65°. Find the perimeter of ABC to one decimal place.
Summarised in our own words. Use the official paper for the exact wording and the diagram.
Solution · 4 marks
- 1In right-angled triangle ADB: AB = 16 ÷ sin 65° = 17.654… cm
- 2AD = 16 ÷ tan 65° = 7.460… cm, so AC = 2 × AD = 14.921… cm
- 3BC = AB because the triangle is isosceles
- 4Perimeter = 17.654… + 17.654… + 14.921… = 50.2 cm
Answer50.2
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