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Date November 2016 Marks available 6 Reference code 16N.2.SL.TZ0.S_10
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term Show that and Find Question number S_10 Adapted from N/A

Question

The following diagram shows the graph of f ( x ) = a sin b x + c , for 0 x 12 .

N16/5/MATME/SP2/ENG/TZ0/10

The graph of f has a minimum point at ( 3 ,   5 ) and a maximum point at ( 9 ,   17 ) .

The graph of g is obtained from the graph of f by a translation of ( k 0 ) . The maximum point on the graph of g has coordinates ( 11.5 ,   17 ) .

The graph of g changes from concave-up to concave-down when x = w .

(i)     Find the value of c .

(ii)     Show that b = π 6 .

(iii)     Find the value of a .

[6]
a.

(i)     Write down the value of k .

(ii)     Find g ( x ) .

[3]
b.

(i)     Find w .

(ii)     Hence or otherwise, find the maximum positive rate of change of g .

[6]
c.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

(i)     valid approach     (M1)

eg 5 + 17 2

c = 11    A1     N2

(ii)     valid approach     (M1)

eg period is 12, per  = 2 π b ,   9 3

b = 2 π 12    A1

b = π 6      AG     N0

(iii)     METHOD 1

valid approach     (M1)

eg 5 = a sin ( π 6 × 3 ) + 11 , substitution of points

a = 6      A1     N2

METHOD 2

valid approach     (M1)

eg 17 5 2 , amplitude is 6

a = 6      A1     N2

[6 marks]

a.

(i)     k = 2.5      A1     N1

(ii)     g ( x ) = 6 sin ( π 6 ( x 2.5 ) ) + 11      A2     N2

[3 marks]

b.

(i)     METHOD 1 Using g

recognizing that a point of inflexion is required     M1

eg sketch, recognizing change in concavity

evidence of valid approach     (M1)

eg g ( x ) = 0 , sketch, coordinates of max/min on  g

w = 8.5 (exact)     A1     N2

METHOD 2 Using f

recognizing that a point of inflexion is required     M1

eg sketch, recognizing change in concavity

evidence of valid approach involving translation     (M1)

eg x = w k , sketch,  6 + 2.5

w = 8.5  (exact)     A1     N2

(ii)     valid approach involving the derivative of g or f (seen anywhere)     (M1)

eg g ( w ) ,   π cos ( π 6 x ) , max on derivative, sketch of derivative

attempt to find max value on derivative     M1

eg π cos ( π 6 ( 8.5 2.5 ) ) ,   f ( 6 ) , dot on max of sketch

3.14159

max rate of change = π  (exact), 3.14     A1     N2

[6 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Topic 4—Statistics and probability » SL 4.1—Concepts, reliability and sampling techniques
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