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Date November 2013 Marks available 5 Reference code 13N.2.hl.TZ0.3
Level HL only Paper 2 Time zone TZ0
Command term Sketch Question number 3 Adapted from N/A

Question

Consider \(f(x) = \ln x - {{\text{e}}^{\cos x}},{\text{ }}0 < x \leqslant 10\).

Sketch the graph of \(y = f(x)\), stating the coordinates of any maximum and minimum points and points of intersection with the x-axis.

[5]
a.

Solve the inequality \(\ln x \leqslant {{\text{e}}^{\cos x}},{\text{ }}0 < x \leqslant 10\).

[2]
b.

Markscheme

 

 

A correct graph shape for \(0 < x \leqslant 10\)     A1

maxima (3.78, 0.882) and (9.70, 1.89)     A1

minimum (6.22, –0.885)     A1

x-axis intercepts (1.97, 0), (5.24, 0) and (7.11, 0)     A2

 

Note:     Award A1 if two x-axis intercepts are correct.

 

[5 marks]

a.

\(0 < x \leqslant 1.97\)     A1

\(5.24 \leqslant x \leqslant 7.11\)     A1

[2 marks]

b.

Examiners report

Part (a) was reasonably well done although more care was required when showing correct endpoint behaviour. A number of sketch graphs suggested the existence of either a vertical axis intercept or displayed an open circle on the vertical axis. A large number of candidates did not state the coordinates of the various key features correct to three significant figures. A large number of candidates did not locate the maximum near \(x = 10\). Most candidates were able to locate the x-axis intercepts and the minimum. A few candidates unfortunately sketched a graph from a GDC set in degrees.

a.

In part (b), a number of candidates identified the correct critical values but used incorrect inequality signs. Some candidates attempted to solve the inequality algebraically.

b.

Syllabus sections

Topic 2 - Core: Functions and equations » 2.2 » The graph of a function; its equation \(y = f\left( x \right)\) .
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