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Date May 2022 Marks available 8 Reference code 22M.1.AHL.TZ1.17
Level Additional Higher Level Paper Paper 1 Time zone Time zone 1
Command term Find Question number 17 Adapted from N/A

Question

A function f is of the form ft=peqcosrt, p, q, r+. Part of the graph of f is shown.

The points A and B have coordinates A(0, 6.5) and B(5.2, 0.2), and lie on f.

The point A is a local maximum and the point B is a local minimum.

Find the value of p, of q and of r.

Markscheme

substitute coordinates of A

f0=peqcos0=6.5

6.5=peq             (A1)


substitute coordinates of B

f5.2=peqcos5.2r=0.2


EITHER

f't=-pqrsinrteqcosrt             (M1)

minimum occurs when -pqrsin5.2reqcos5.2r=0

sinrt=0

r×5.2=π             (A1)


OR

minimum value occurs when cosrt=-1             (M1)

r×5.2=π             (A1)


OR

period =2×5.2=10.4             (A1)

r=2π10.4             (M1)


THEN

r=π5.2=0.604152 0.604             A1

0.2=pe-q             (A1)

eliminate p or q             (M1)

e2q=6.50.2   OR   0.2=p26.5

q=1.74 1.74062             A1

p=1.14017  1.14             A1

 

[8 marks]

Examiners report

This was a challenging question and suitably positioned at the end of the examination. Candidates who attempted it were normally able to substitute points A and B into the given equation. Some were able to determine the first derivative. Only a few candidates were able to earn significant marks for this question.

Syllabus sections

Topic 5—Calculus » SL 5.6—Stationary points, local max and min
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