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Date May 2017 Marks available 6 Reference code 17M.1.SL.TZ1.S_10
Level Standard Level Paper Paper 1 (without calculator) Time zone Time zone 1
Command term Find Question number S_10 Adapted from N/A

Question

The following table shows the probability distribution of a discrete random variable A , in terms of an angle θ .

M17/5/MATME/SP1/ENG/TZ1/10

Show that cos θ = 3 4 .

[6]
a.

Given that tan θ > 0 , find tan θ .

[3]
b.

Let y = 1 cos x , for 0 < x < π 2 . The graph of y between x = θ and  x = π 4 is rotated 360° about the x -axis. Find the volume of the solid formed.

[6]
c.

Markscheme

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

evidence of summing to 1     (M1)

eg p = 1

correct equation     A1

eg cos θ + 2 cos 2 θ = 1

correct equation in cos θ     A1

eg cos θ + 2 ( 2 cos 2 θ 1 ) = 1 ,   4 cos 2 θ + cos θ 3 = 0

evidence of valid approach to solve quadratic     (M1)

eg factorizing equation set equal to 0 ,   1 ± 1 4 × 4 × ( 3 ) 8

correct working, clearly leading to required answer     A1

eg ( 4 cos θ 3 ) ( cos θ + 1 ) ,   1 ± 7 8

correct reason for rejecting cos θ 1     R1

eg cos θ is a probability (value must lie between 0 and 1), cos θ > 0

 

Note:     Award R0 for cos θ 1 without a reason.

 

cos θ = 3 4    AG  N0

a.

valid approach     (M1)

eg sketch of right triangle with sides 3 and 4, sin 2 x + cos 2 x = 1

correct working     

(A1)

eg missing side = 7 ,   7 4 3 4

tan θ = 7 3     A1     N2

[3 marks]

b.

attempt to substitute either limits or the function into formula involving f 2     (M1)

eg π θ π 4 f 2 ,   ( 1 cos x ) 2

correct substitution of both limits and function     (A1)

eg π θ π 4 ( 1 cos x ) 2 d x

correct integration     (A1)

eg tan x

substituting their limits into their integrated function and subtracting     (M1)

eg tan π 4 tan θ

 

Note:     Award M0 if they substitute into original or differentiated function.

 

tan π 4 = 1     (A1)

eg 1 tan θ

V = π π 7 3     A1     N3

 

[6 marks]

c.

Examiners report

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

Syllabus sections

Topic 5 —Calculus » SL 5.5—Integration introduction, areas between curve and x axis
Show 162 related questions
Topic 3— Geometry and trigonometry » SL 3.6—Pythagorean identity, double angles
Topic 4—Statistics and probability » SL 4.7—Discrete random variables
Topic 2—Functions » SL 2.7—Solutions of quadratic equations and inequalities, discriminant and nature of roots
Topic 2—Functions » SL 2.10—Solving equations graphically and analytically
Topic 5 —Calculus » SL 5.11—Definite integrals, areas under curve onto x-axis and areas between curves
Topic 2—Functions
Topic 3— Geometry and trigonometry
Topic 4—Statistics and probability
Topic 5 —Calculus

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