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 AˆOB=1.9 radians.
Find the length of the chord [AB].
Find the area of the shaded sector.
Markscheme
EITHER
uses the cosine rule (M1)
AB2=52+52-2×5×5×cos 1.9 (A1)
OR
uses right-angled trigonometry (M1)
AB25sin 0.95 (A1)
OR
uses the sine rule (M1)
α=12(π-1.9)(=0.6207…)
ABsin 1.9=5sin 0.6207… (A1)
THEN
AB=8.13415…
AB=8.13 (m) A1
[3 marks]
let the shaded area be A
METHOD 1
attempt at finding reflex angle (M1)
AˆOB=2π-1.9
substitution into area formula (A1)
OR
A1
METHOD 2
let the area of the circle be and the area of the unshaded sector be
(M1)
(A1)
A1
[3 marks]
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.