Date | May 2021 | Marks available | 1 | Reference code | 21M.2.SL.TZ1.2 |
Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 1 |
Command term | Write down | Question number | 2 | Adapted from | N/A |
Question
The diagram below shows a circular clockface with centre O. The clock’s minute hand has a length of 10 cm. The clock’s hour hand has a length of 6 cm.
At 4:00 pm the endpoint of the minute hand is at point A and the endpoint of the hour hand is at point B.
Between 4:00 pm and 4:13 pm, the endpoint of the minute hand rotates through an angle, θ, from point A to point C. This is illustrated in the diagram.
A second clock is illustrated in the diagram below. The clock face has radius 10 cm with minute and hour hands both of length 10 cm. The time shown is 6:00 am. The bottom of the clock face is located 3 cm above a horizontal bookshelf.
The height, h centimetres, of the endpoint of the minute hand above the bookshelf is modelled by the function
h(θ)=10 cos θ+13, θ≥0,
where θ is the angle rotated by the minute hand from 6:00 am.
The height, g centimetres, of the endpoint of the hour hand above the bookshelf is modelled by the function
g(θ)=-10 cos(θ12)+13, θ≥0,
where θ is the angle in degrees rotated by the minute hand from 6:00 am.
Find the size of angle AˆOB in degrees.
Find the distance between points A and B.
Find the size of angle θ in degrees.
Calculate the length of arc AC.
Calculate the area of the shaded sector, AOC.
Write down the height of the endpoint of the minute hand above the bookshelf at 6:00 am.
Find the value of h when θ=160°.
Write down the amplitude of g(θ).
The endpoints of the minute hand and hour hand meet when θ=k.
Find the smallest possible value of k.
Markscheme
4×360°12 OR 4×30° (M1)
120° A1
[2 marks]
substitution in cosine rule (M1)
AB2=102+62-2×10×6×cos(120°) (A1)
AB=14 cm A1
Note: Follow through marks in part (b) are contingent on working seen.
[3 marks]
θ=13×6 (M1)
=78° A1
[2 marks]
substitution into the formula for arc length (M1)
l=78360×2×π×10 OR l=13π30×10
=13.6 cm (13.6135…, 4.33π, 13π3) A1
[2 marks]
substitution into the area of a sector (M1)
A=78360×π×102 OR l=12×13π30×102
=68.1 cm2 (68.0678…, 21.7π, 65π3) A1
[2 marks]
23 A1
[1 mark]
correct substitution (M1)
h=10 cos(160°)+13
=3.60 cm (3.60307…) A1
[2 marks]
10 A1
[1 mark]
EITHER
10×cos(θ)+13=-10×cos(θ12)+13 (M1)
OR
(M1)
Note: Award M1 for equating the functions. Accept a sketch of h(θ) and g(θ) with point(s) of intersection marked.
THEN
k=196° (196.363…) A1
Note: The answer 166.153… is incorrect but the correct method is implicit. Award (M1)A0.
[2 marks]