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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
for the guidance of teachers
9709 MATHEMATICS
9709/13
Paper 1, maximum raw mark 75
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.
Mark schemes must be read in conjunction with the question papers and the report on the
examination.
• Cambridge will not enter into discussions or correspondence in connection with these mark schemes.
Cambridge is publishing the mark schemes for the May/June 2012 question papers for most IGCSE,
GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level
syllabuses.
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MARK SCHEME for the May/June 2012 question paper
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er
GCE Advanced Subsidiary Level and GCE Advanced Level
Page 2
Mark Scheme: Teachers’ version
GCE AS/A LEVEL – May/June 2012
Syllabus
9709
Paper
13
Mark Scheme Notes
Marks are of the following three types:
M
Method mark, awarded for a valid method applied to the problem. Method marks are
not lost for numerical errors, algebraic slips or errors in units. However, it is not usually
sufficient for a candidate just to indicate an intention of using some method or just to
quote a formula; the formula or idea must be applied to the specific problem in hand,
e.g. by substituting the relevant quantities into the formula. Correct application of a
formula without the formula being quoted obviously earns the M mark and in some
cases an M mark can be implied from a correct answer.
A
Accuracy mark, awarded for a correct answer or intermediate step correctly obtained.
Accuracy marks cannot be given unless the associated method mark is earned (or
implied).
B
Mark for a correct result or statement independent of method marks.
•
When a part of a question has two or more "method" steps, the M marks are generally
independent unless the scheme specifically says otherwise; and similarly when there are
several B marks allocated. The notation DM or DB (or dep*) is used to indicate that a
particular M or B mark is dependent on an earlier M or B (asterisked) mark in the scheme.
When two or more steps are run together by the candidate, the earlier marks are implied and
full credit is given.
•
The symbol √ implies that the A or B mark indicated is allowed for work correctly following
on from previously incorrect results. Otherwise, A or B marks are given for correct work only.
A and B marks are not given for fortuitously "correct" answers or results obtained from
incorrect working.
•
Note:
B2 or A2 means that the candidate can earn 2 or 0.
B2/1/0 means that the candidate can earn anything from 0 to 2.
The marks indicated in the scheme may not be subdivided. If there is genuine doubt whether
a candidate has earned a mark, allow the candidate the benefit of the doubt. Unless
otherwise indicated, marks once gained cannot subsequently be lost, e.g. wrong working
following a correct form of answer is ignored.
•
Wrong or missing units in an answer should not lead to the loss of a mark unless the
scheme specifically indicates otherwise.
•
For a numerical answer, allow the A or B mark if a value is obtained which is correct to 3 s.f.,
or which would be correct to 3 s.f. if rounded (1 d.p. in the case of an angle). As stated
above, an A or B mark is not given if a correct numerical answer arises fortuitously from
incorrect working. For Mechanics questions, allow A or B marks for correct answers which
arise from taking g equal to 9.8 or 9.81 instead of 10.
© University of Cambridge International Examinations 2012
Page 3
Mark Scheme: Teachers’ version
GCE AS/A LEVEL – May/June 2012
Syllabus
9709
Paper
13
The following abbreviations may be used in a mark scheme or used on the scripts:
AEF
Any Equivalent Form (of answer is equally acceptable)
AG
Answer Given on the question paper (so extra checking is needed to ensure that
the detailed working leading to the result is valid)
BOD
Benefit of Doubt (allowed when the validity of a solution may not be absolutely
clear)
CAO
Correct Answer Only (emphasising that no "follow through" from a previous error
is allowed)
CWO
Correct Working Only - often written by a ‘fortuitous' answer
ISW
Ignore Subsequent Working
MR
Misread
PA
Premature Approximation (resulting in basically correct work that is insufficiently
accurate)
SOS
See Other Solution (the candidate makes a better attempt at the same question)
SR
Special Ruling (detailing the mark to be given for a specific wrong solution, or a
case where some standard marking practice is to be varied in the light of a
particular circumstance)
Penalties
MR -1
A penalty of MR -1 is deducted from A or B marks when the data of a question or
part question are genuinely misread and the object and difficulty of the question
remain unaltered. In this case all A and B marks then become "follow through √"
marks. MR is not applied when the candidate misreads his own figures - this is
regarded as an error in accuracy. An MR-2 penalty may be applied in particular
cases if agreed at the coordination meeting.
PA -1
This is deducted from A or B marks in the case of premature approximation. The
PA -1 penalty is usually discussed at the meeting.
© University of Cambridge International Examinations 2012
Page 4
1
Mark Scheme: Teachers’ version
GCE AS/A LEVEL – May/June 2012
tan 2 θ − sin 2 θ = tan 2 θ sin 2 θ
s2
− s2
(i)
2
c
s 2 (1 − c 2 )
s 2 − s 2c 2
=
→
c2
c2
→ t 2s2
Syllabus
9709
M1
Use of s ÷ c = t
M1
Use of s² + c² = 1
Paper
13
All ok
A1
[3]
(ii) RHS > 0 → tan² θ > sin ²θ QED
tan θ > sin θ if θ acute.
Realises RHS > 0
B1
[1]
2
 2
 4 
1
 
 
 
OA =  − 1 , OB =  2  , OC =  3  .
 4
 − 2
 p
 
 
 
 2 
 
(i) AB =  3  Modulus = (4 + 9 + 36 )
 − 6
 
 2 
1 
Unit Vector =  3 
7 
 − 6
(ii) OB.OC = 4 + 6 − 2 p
=0 → p=5
co. Correct method for modulus
B1 M1
co for his vector AB.
A1
[3]
Dot product = 0. co
M1A1
[2]
3
(1 − 2 x) 2 (1 + ax)6
Coeff of x in (1 + ax) 6 = 6ax
B1
B1
6C1 needs removing (here or later)
6C2 needs removing (here or later)
Multiplies by (1 − 4x + 4x²)
2 terms in x 6a − 4 = −1
→ a=½
M1
A1
Needs to consider 2 terms in equation
Co
3 terms in x² 15a² − 24a + 4 = b
→ b = −4¼
M1
A1
Needs to consider 3 terms in equation
Coeff of x² in (1 + ax) 6 = 15a²x²
[6]
4
sin 2 x + 3 cos 2 x = 0
(i) → tan 2x = −3
2x = 180 – 71.6 or 360 – 71.6
x = 54.2º or 144.2º
Also 234.2º and 324.2º
Uses tan2x = k and works with “2x”.
Finds “2x” before ÷ 2
co. co (both of these need 2nd M)
for 180º + his answer(s)
M1
M1
A1A1
A1
[5]
(ii) 12 answers.
for 3 times the number of solns to (i).
B1
[1]
© University of Cambridge International Examinations 2012
Page 5
5
Mark Scheme: Teachers’ version
GCE AS/A LEVEL – May/June 2012
8
− 2 ; at x = 0, y = 2
y2
64 32
→ x2 = 4 − 2 + 4
y
y
x=
64 y −3 32 y −1
−
+ 4y
−3
−1
Uses limits 1 to 2
→ 6⅔π
Integral of x² =
Syllabus
9709
B1
co
B1B1B1
All co.
M1
A1
Uses 1 to 2 or 2 to 1.
co.
Paper
13
[6]
6
7
(i) Uses Sn
9
(24 + 8d ) = 135 → d = ¾
2
Uses correct formula
co
M1
A1
[2]
B1
on “d”
(ii) 9th term of AP = 12 + 8×¾ = 18
GP 1st tern 12, 2nd term 18
Common ratio = r = 18 ÷ 12 = 1½
3rd term of GP = ar² = 27
nth term of AP is 12 + (n − 1)¾
12 + (n − 1)¾ = 27 → n = 21
M1
M1
Uses “ar”
Uses ar² or “ar” × r
M1A1
Links AP with GP. co
10
−2
2x + 1
dy
− 10
(i)
=
×2
dx
(2 x + 1) 2
At A, y = 0, → x = 2
4
m at x = 2, is −
5
Eqn of tangent is y = − 54 ( x − 2)
B1 B1
Without the “×2”. For the “×2”.
B1
For x = 2
M1
A1
Must be using differential as m
co – answer given.
[5]
y=
→ 5y + 4x = 8
[5]
(ii) C (0, 1.6)
d=
8
(1.6
2
)
+ 2 2 = 2.56
[2]
(i) OBX = 90º, cos θ =
r
2r
→ θ = ⅓ π.
P = r + (⅓ rπ + r 3 )
1
2
Needs 90º + cos (or Pyth + sin or tan)
co ag
M1
A1
[2]
(ii) Arc length AB = ⅓ rπ
BX = rtan(⅓π) = r 3
(iii) Area =
Correct method – needs . co
M1 A1
r 2 3 − 16 r 2π
r + sum of other two
B1
B1
B1
[3]
B1 B1
on tan(⅓π). co
[2]
© University of Cambridge International Examinations 2012
Page 6
9
Mark Scheme: Teachers’ version
GCE AS/A LEVEL – May/June 2012
d2 y
= − 4x
dx 2
dy
= − 2x 2 + c
(i)
dx
dy
= 0 when x = 2, → c = 8
dx
2 x3
y=−
+ 8 x (+C)
3
4
Subs (2, 12) → C =
3
(iii)
dy
dy
dx
=
×
dx
dt
dt
= −10 × 0.05
→ decreasing at 0.5 units per second
Syllabus
9709
B1
For −2x²
B1
c=8
B1 B1
For each term –
Paper
13
on “c”– ignore (+C)
Uses (2, 12) to find C.
M1 A1
[6]
M1
Must use. Enough to see product of
gradient and rate. bod over notation.
A1
[2]
10
2y + x = k
xy = 6
(i) 2 y + x = 8 → y (8 − 2 y ) = 6
2 y 2 − 8 y + 6 = 0 or x² − 8x + 12 = 0
→(6, 1) and (2, 3)
Midpoint M (4, 2)
m = −½
Perpendicular m = 2
→ y − 2 = 2( x − 4)
M1
Complete elimination of x (or y)
DM1A1
DM1 soln of quadratic. co
M1
for their 2 points
M1
A1
Uses m1m2 = −1 to find perp. gradient
co unsimplified
[6]
(ii) (k − 2 y ) y = 6
→ 2 y 2 − ky + 6 = 0 or x² − kx + 12 = 0
Uses b² − 4ac (0)
→ k² > 48
→ k < − 48 and k > 48
Any use of b² − 4ac on a quadratic = 0
For √48 on its own
All correct.
M1
A1
A1
[3]
© University of Cambridge International Examinations 2012
Page 7
Mark Scheme: Teachers’ version
GCE AS/A LEVEL – May/June 2012
Syllabus
9709
Paper
13
11 f(x) = 8 − ( x − 2) 2 ,
(i) Stationary point at x = 2
y – coordinate = 8
Nature Maximum
(or y y = − x 2 + 4 x + 4
−2x + 4 = 0 → (2, 8) Max)
B1
B1
B1
(ii) k = 2
B1
co
co
co independent of first two marks
[3]
on “x-value”
[1]
(iii) y = 8 − ( x − 2) 2
→ ( x − 2) 2 + y = 8
M1
Attempt to make x the subject
→ (x − 2) = ± 8 − y
M1
Order of operations correct
→ g
–1
= 2 + 8− x
A1
Must be f(x).
[3]
(iv)
B1 arc 1st quad (no tp, no axes)
B1 Evidence of symmetry about y = x
B1 all correct as shown left
B1
B1
B1
[3]
© University of Cambridge International Examinations 2012