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Date May 2018 Marks available 7 Reference code 18M.2.SL.TZ1.S_6
Level Standard Level Paper Paper 2 Time zone Time zone 1
Command term Find Question number S_6 Adapted from N/A

Question

Triangle ABC has a = 8.1 cm, b = 12.3 cm and area 15 cm2. Find the largest possible perimeter of triangle ABC.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

correct substitution into the formula for area of a triangle      (A1)

eg  15 =  1 2 × 8.1 × 12.3 × sin C

correct working for angle C    (A1)

eg  sin C = 0.301114, 17.5245…, 0.305860

recognizing that obtuse angle needed      (M1)

eg  162.475, 2.83573, cos C < 0

evidence of choosing the cosine rule      (M1)

eg  a2 = b2 + c2 − 2bc cos(A)

correct substitution into cosine rule to find c     (A1)

eg  c2 = (8.1)2 + (12.3)2 − 2(8.1)(12.3) cos C

c = 20.1720    (A1)

8.1 + 12.3 + 20.1720 = 40.5720

perimeter = 40.6    A1 N4

[7 marks]

Examiners report

[N/A]

Syllabus sections

Topic 3— Geometry and trigonometry » SL 3.5—Unit circle definitions of sin, cos, tan. Exact trig ratios, ambiguous case of sine rule
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Topic 3— Geometry and trigonometry

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