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Date May 2022 Marks available 3 Reference code 22M.2.SL.TZ2.1
Level Standard Level Paper Paper 2 Time zone Time zone 2
Command term Find Question number 1 Adapted from N/A

Question

The following diagram shows a circle with centre O and radius 5 metres.

Points A and B lie on the circle and AO^B=1.9 radians.

Find the length of the chord [AB].

[3]
a.

Find the area of the shaded sector.

[3]
b.

Markscheme

EITHER

uses the cosine rule           (M1)

AB2=52+52-2×5×5×cos1.9           (A1)


OR

uses right-angled trigonometry           (M1)

AB25sin0.95           (A1)


OR

uses the sine rule           (M1)

α=12π-1.9=0.6207

ABsin1.9=5sin0.6207           (A1)


THEN

AB=8.13415

AB=8.13m           A1

 

[3 marks]

a.

let the shaded area be A


METHOD 1

attempt at finding reflex angle           (M1)

AO^B=2π-1.9 =4.3831

substitution into area formula           (A1)

A=12×52×4.3831  OR  2π-1.92π×π52

=54.7898

=54.8m2           A1

 

METHOD 2

let the area of the circle be AC and the area of the unshaded sector be AU

A=AC-AU           (M1)

A=π×52-12×52×1.9  =78.5398-23.75           (A1)

=54.7898

=54.8m2           A1

 

[3 marks]

b.

Examiners report

Most students used the cosine rule to correctly find AB in part (a), although many found the arc length instead of the chord.

Part (b) was generally correctly solved. Some candidates found the area of the unshaded region rather than the shaded one.

a.
[N/A]
b.

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 » SL 3.4—Circle: radians, arcs, sectors
Topic 3— Geometry and trigonometry

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