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Date May 2019 Marks available 3 Reference code 19M.1.SL.TZ1.S_3
Level Standard Level Paper Paper 1 (without calculator) Time zone Time zone 1
Command term Find Question number S_3 Adapted from N/A

Question

The following diagram shows a right triangle ABC. Point D lies on AB such that CD bisects AĈB.

AĈD = θ and AC = 14 cm

Given that sinθ=35, find the value of cosθ.

[3]
a.

Find the value of cos2θ.

[3]
b.

Hence or otherwise, find BC.

[2]
c.

Markscheme

valid approach       (M1)

eg      labelled sides on separate triangle, sin2x+cos2x=1

correct working       (A1)

eg      missing side is 4, 1(35)2

cosθ=45                          A1   N3

[3 marks]

a.

correct substitution into cos2θ       (A1)

eg      2(1625)1,  12(35)2,  1625925

cos2θ=725                         A1   N2

[2 marks]

b.

correct working      (A1)

eg      725=14BCBC=14×257

BC=50 (cm)                        A1   N2

[2 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Topic 3— Geometry and trigonometry » SL 3.2—2d and 3d trig, sine rule, cosine rule, area
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Topic 3— Geometry and trigonometry

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