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Date May 2021 Marks available 2 Reference code 21M.1.AHL.TZ2.12
Level Additional Higher Level Paper Paper 1 Time zone Time zone 2
Command term Find Question number 12 Adapted from N/A

Question

It is given that z1=3 cis3π4 and z2=2 cisnπ16, n+.

In parts (a)(i) and (a)(ii), give your answers in the form reiθ, r0, π<θπ.

Find the value of z13.

[2]
a.i.

Find the value of z1z24 for n=2.

[3]
a.ii.

Find the least value of n such that z1z2+.

[3]
b.

Markscheme

z13=27e4 =27e0.785398i                A1A1


Note: Award A1 for 27 and A1 for the angle in the correct form.


[2 marks]

a.i.

z1z24=8116e2 =5.0625e1.57079i                A1A2


Note: Award A1 for 8116, A2 for the angle in the correct form and A1 for the angle in incorrect form e.g. cisπ2 and/or 5π2. Award A1 if i is given in place of cisπ2.


[3 marks]

a.ii.

z1z2=6cis3π4+nπ16                (M1)

=6cis12π+nπ16

12π+nπ=32π                (M1)

n=20                A1


[3 marks]

b.

Examiners report

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

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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