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Date May 2018 Marks available 2 Reference code 18M.2.AHL.TZ2.H_1
Level Additional Higher Level Paper Paper 2 Time zone Time zone 2
Command term Express Question number H_1 Adapted from N/A

Question

Consider the complex number z=2+7i6+2i.

Express z in the form a+ib, where a,bQ.

[2]
a.

Find the exact value of the modulus of z.

[2]
b.

Find the argument of z, giving your answer to 4 decimal places.

[2]
c.

Markscheme

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

z=(2+7i)(6+2i)×(62i)(62i)     (M1)

=26+38i40=(13+19i20=0.65+0.95i)     A1

[2 marks]

a.

attempt to use |z|=a2+b2    (M1)

|z|=5340(=53020) or equivalent      A1

Note: A1 is only awarded for the correct exact value.

[2 marks]

b.

EITHER

arg z = arg(2 + 7i) − arg(6 + 2i)      (M1)

OR

arg z = arctan(1913)         (M1)

THEN

arg z = 0.9707 (radians) (= 55.6197 degrees)     A1

Note: Only award the last A1 if 4 decimal places are given.

[2 marks]

c.

Examiners report

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

Syllabus sections

Topic 1—Number and algebra » AHL 1.13—Polar and Euler form
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Topic 1—Number and algebra

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