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Date May 2021 Marks available 3 Reference code 21M.3.AHL.TZ1.1
Level Additional Higher Level Paper Paper 3 Time zone Time zone 1
Command term Write down Question number 1 Adapted from N/A

Question

A suitable site for the landing of a spacecraft on the planet Mars is identified at a point, A. The shortest time from sunrise to sunset at point A must be found.

Radians should be used throughout this question. All values given in the question should be treated as exact.

Mars completes a full orbit of the Sun in 669 Martian days, which is one Martian year.

On day t, where t , the length of time, in hours, from the start of the Martian day until sunrise at point A can be modelled by a function, R(t), where

R(t)=asinbt+c, t.

The graph of R is shown for one Martian year.

Mars completes a full rotation on its axis in 24 hours and 40 minutes.

The time of sunrise on Mars depends on the angle, δ, at which it tilts towards the Sun. During a Martian year, δ varies from 0.440 to 0.440 radians.

The angle, ω, through which Mars rotates on its axis from the start of a Martian day to the moment of sunrise, at point A, is given by cosω=0.839tanδ, 0ωπ.

Use your answers to parts (b) and (c) to find

Let S(t) be the length of time, in hours, from the start of the Martian day until sunset at point A on day t. S(t) can be modelled by the function

S(t)=1.5sin(0.00939t+2.83)+18.65.

The length of time between sunrise and sunset at point A, L(t), can be modelled by the function

L(t)=1.5sin(0.00939t+2.83)1.6sin(0.00939t)+d.

Let f(t)=1.5sin(0.00939t+2.83)1.6sin(0.00939t) and hence L(t)=f(t)+d.

f(t) can be written in the form Im(z1z2) , where z1 and z2 are complex functions of t.

Show that b0.00939.

[2]
a.

Find the angle through which Mars rotates on its axis each hour.

[3]
b.

Show that the maximum value of ω=1.98, correct to three significant figures.

[3]
c.i.

Find the minimum value of ω.

[1]
c.ii.

the maximum value of R(t).

[2]
d.i.

the minimum value of R(t).

[1]
d.ii.

Hence show that a=1.6, correct to two significant figures.

[2]
e.

Find the value of c.

[2]
f.

Find the value of d.

[2]
g.

Write down z1 and z2 in exponential form, with a constant modulus.

[3]
h.i.

Hence or otherwise find an equation for L in the form L(t)=psin(qt+r)+d, where p, q, r, d.

[4]
h.ii.

Find, in hours, the shortest time from sunrise to sunset at point A that is predicted by this model.

[2]
h.iii.

Markscheme

recognition that period =669                  (M1)

b=2π669  OR  b=0.00939190                A1


Note:
Award A1 for a correct expression leading to the given value or for a correct value of b to 4 sf or greater accuracy.


b0.00939             AG


[2 marks]

a.

length of day=2423 hours                (A1)


Note: Award A1 for 23, 0.666, 0.6¯ or 0.667.


2π2423               (M1)


Note: Accept 3602423.


=0.255 radians 0.254723, 3π37, 14.5945°               A1

[3 marks]

b.

substitution of either value of δ into equation              (M1)

correct use of arccos to find a value for ω              (M1)


Note: Both (M1) lines may be seen in either part (c)(i) or part (c)(ii).


cosω=0.839tan-0.440               A1

ω=1.97684

1.98               AG


Note: For substitution of 1.98 award M0A0.

 

[3 marks]

c.i.

δ=0.440

ω=1.16  (1.16474)            A1

 

[1 mark]

c.ii.

Rmax=1.976840.25472           (M1)

=7.76 hours  (7.76075)            A1


Note: Accept 7.70 from use of 1.98.

[2 marks]

d.i.

Rmin=1.164740.25472

=4.57 hours  (4.57258)            A1


Note: Accept 4.55 and 4.56 from use of rounded values.

[1 mark]

d.ii.

a=7.76075-4.572582           M1

1.59408           A1


Note: Award M1 for substituting their values into a correct expression. Award A1 for a correct value of a from their expression which has at least 3 significant figures and rounds correctly to 1.6.

1.6 (correct to 2 sf)          AG

 

[2 marks]

e.

EITHER

c=7.76075+4.572582 =12.3332           (M1)


OR

c=4.57258+1.59408  or  c=7.76075-1.59408


THEN

=6.17  6.16666           A1


Note: Accept 6.16 from use of rounded values. Follow through on their answers to part (d) and 1.6.


[2 marks]

f.

d=18.65-6.16666           (M1)

=12.5  12.4833           A1


Note: Follow through for 18.65 minus their answer to part (f).


[2 marks]

g.

at least one expression in the form regti           (M1)

z1=1.5e0.00939t+2.83i,  z2=1.6e0.00939ti           A1A1


[3 marks]

h.i.

EITHER

z1-z2=1.5e0.00939t+2.83i-1.6e0.00939ti

=e0.00939ti1.5e2.83i-1.6               (M1)

=e0.00939ti3.06249e2.99086i            (A1)(A1)


OR

graph of L or f

p=3.06249...            (A1)

r=-0.150729...  OR  r=2.99086...            (M1)(A1)


Note: The p and r variables (or equivalent) must be seen.


THEN

L(t)=3.06sin(0.00939t+2.99)+12.5                 A1

L(t)=3.06248sin(0.00939t+2.99086)+12.4833


Note: Accept equivalent forms, e.g. L(t)=3.06sin(0.00939t-0.151)+12.5.
Follow through on their answer to part (g) replacing 12.5.

 
[4 marks]

h.ii.

shortest time between sunrise and sunset

12.4833-3.06249               (M1)

=9.42 hours  9.420843                 A1


Note:
Accept 9.44 from use of 3 sf values.

[2 marks]

h.iii.

Examiners report

[N/A]
a.
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b.
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c.i.
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c.ii.
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d.i.
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d.ii.
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e.
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f.
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g.
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h.i.
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h.ii.
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h.iii.

Syllabus sections

Topic 1—Number and algebra » AHL 1.13—Polar and Euler form
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Topic 1—Number and algebra

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