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Date November 2016 Marks available 2 Reference code 16N.2.hl.TZ0.5
Level HL only Paper 2 Time zone TZ0
Command term State Question number 5 Adapted from N/A

Question

Consider the function \(f\) defined by \(f(x) = 3x\arccos (x)\) where \( - 1 \leqslant x \leqslant 1\).

Sketch the graph of \(f\) indicating clearly any intercepts with the axes and the coordinates of any local maximum or minimum points.

[3]
a.

State the range of \(f\).

[2]
b.

Solve the inequality \(\left| {3x\arccos (x)} \right| > 1\).

[4]
c.

Markscheme

N16/5/MATHL/HP2/ENG/TZ0/05.a/M

correct shape passing through the origin and correct domain     A1

 

Note: Endpoint coordinates are not required. The domain can be indicated by \( - 1\) and 1 marked on the axis.

\((0.652,{\text{ }}1.68)\)    A1

two correct intercepts (coordinates not required)     A1

 

Note: A graph passing through the origin is sufficient for \((0,{\text{ }}0)\).

 

[3 marks]

a.

\([-9.42,{\text{ }}1.68]{\text{ }}({\text{or }} - 3\pi ,{\text{ }}1.68])\)    A1A1

 

Note: Award A1A0 for open or semi-open intervals with correct endpoints. Award A1A0 for closed intervals with one correct endpoint.

 

[2 marks]

b.

attempting to solve either \(\left| {3x\arccos (x)} \right| > 1\) (or equivalent) or \(\left| {3x\arccos (x)} \right| = 1\) (or equivalent) (eg. graphically)     (M1)

N16/5/MATHL/HP2/ENG/TZ0/05.c/M

\(x =  - 0.189,{\text{ }}0.254,{\text{ }}0.937\)    (A1)

\( - 1 \leqslant x <  - 0.189{\text{ or }}0.254 < x < 0.937\)    A1A1

 

Note: Award A0 for \(x <  - 0.189\).

 

[4 marks]

c.

Examiners report

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

Syllabus sections

Topic 3 - Core: Circular functions and trigonometry » 3.5 » The inverse functions \(x \mapsto \arcsin x\) , \(x \mapsto \arccos x\) , \(x \mapsto \arctan x\) ; their domains and ranges; their graphs.

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