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Date May 2008 Marks available 2 Reference code 08M.1.sl.TZ1.7
Level SL only Paper 1 Time zone TZ1
Command term Calculate Question number 7 Adapted from N/A

Question

Triangle ABC is such that AC is 7 cm, angle ABC is 65 and angle ACB is 30.

Sketch the triangle writing in the side length and angles.

[1]
a.

Calculate the length of AB.

[2]
b.

Find the area of triangle ABC.

[3]
c.

Markscheme

     (A1)     (C1)


Note: (A1) for fully labelled sketch.

[1 mark]

a.

Unit penalty (UP) may apply in this question.

ABsin30=7sin65     (M1)

(UP)     AB=3.86 cm     (A1)(ft)     (C2)

Note: (M1) for use of sine rule with correct values substituted.

[2 marks]

b.

Unit penalty (UP) may apply in this question.

Angle BAC=85     (A1)

Area=12×7×3.86×sin85     (M1)

(UP)     =13.5 cm2     (A1)(ft)     (C3)

[3 marks]

c.

Examiners report

The triangle was drawn correctly by most and a majority correctly found the length of AB - a few did not write down the units (cm) and so lost a Unit penalty mark. There was still a significant number who tried to use right-angled trigonometry to find the length.

Finding the area of the triangle was mixed with many again assuming the existence of a right angle. Some candidates had their calculators in radian mode rather than degree mode.

a.

The triangle was drawn correctly by most and a majority correctly found the length of AB - a few did not write down the units (cm) and so lost a Unit penalty mark. There was still a significant number who tried to use right-angled trigonometry to find the length.

Finding the area of the triangle was mixed with many again assuming the existence of a right angle. Some candidates had their calculators in radian mode rather than degree mode.

b.

The triangle was drawn correctly by most and a majority correctly found the length of AB - a few did not write down the units (cm) and so lost a Unit penalty mark. There was still a significant number who tried to use right-angled trigonometry to find the length.

Finding the area of the triangle was mixed with many again assuming the existence of a right angle. Some candidates had their calculators in radian mode rather than degree mode.

c.

Syllabus sections

Topic 5 - Geometry and trigonometry » 5.3 » Use of the sine rule: asinA=bsinB=csinC.
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