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Date May 2018 Marks available 3 Reference code 18M.1.SL.TZ1.S_5
Level Standard Level Paper Paper 1 (without calculator) Time zone Time zone 1
Command term Find Question number S_5 Adapted from N/A

Question

Let  f ( x ) = 1 2 x 1 , for x > 1 2 .

Find ( f ( x ) ) 2 d x .

[3]
a.

Part of the graph of f is shown in the following diagram.

The shaded region R is enclosed by the graph of f, the x-axis, and the lines x = 1 and x = 9 . Find the volume of the solid formed when R is revolved 360° about the x-axis.

[4]
b.

Markscheme

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

correct working      (A1)

eg    1 2 x 1 d x , ( 2 x 1 ) 1 , 1 2 x 1 , ( 1 u ) 2 d u 2

( f ( x ) ) 2 d x = 1 2 ln ( 2 x 1 ) + c       A2 N3

Note: Award A1 for  1 2 ln ( 2 x 1 ) .

[3 marks]

a.

attempt to substitute either limits or the function into formula involving f 2 (accept absence of π / dx)     (M1)

eg    1 9 y 2 d x , π ( 1 2 x 1 ) 2 d x , [ 1 2 ln ( 2 x 1 ) ] 1 9

substituting limits into their integral and subtracting (in any order)     (M1)

eg   π 2 ( ln ( 17 ) ln ( 1 ) ) , π ( 0 1 2 ln ( 2 × 9 1 ) )

correct working involving calculating a log value or using log law     (A1)

eg   ln ( 1 ) = 0 , ln ( 17 1 )

π 2 ln 17 ( accept  π ln 17 )     A1 N3

Note: Full FT may be awarded as normal, from their incorrect answer in part (a), however, do not award the final two A marks unless they involve logarithms.

[4 marks]

b.

Examiners report

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

Syllabus sections

Topic 5 —Calculus » SL 5.5—Integration introduction, areas between curve and x axis
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