User interface language: English | Español

Date May 2018 Marks available 3 Reference code 18M.1.AHL.TZ1.H_11
Level Additional Higher Level Paper Paper 1 (without calculator) Time zone Time zone 1
Command term Express Question number H_11 Adapted from N/A

Question

Consider  w = 2 ( cos π 3 + i sin π 3 )

These four points form the vertices of a quadrilateral, Q.

Express w2 and w3 in modulus-argument form.

[3]
a.i.

Sketch on an Argand diagram the points represented by w0 , w1 , w2 and w3.

[2]
a.ii.

Show that the area of the quadrilateral Q is  21 3 2 .

[3]
b.

Let z = 2 ( cos π n + i sin π n ) , n Z + . The points represented on an Argand diagram by  z 0 , z 1 , z 2 , , z n  form the vertices of a polygon  P n .

Show that the area of the polygon  P n  can be expressed in the form  a ( b n 1 ) sin π n , where  a , b R .

[6]
c.

Markscheme

w 2 = 4 cis ( 2 π 3 ) ; w 3 = 8 cis ( π )      (M1)A1A1

Note: Accept Euler form.

Note: M1 can be awarded for either both correct moduli or both correct arguments.

Note: Allow multiplication of correct Cartesian form for M1, final answers must be in modulus-argument form.

[3 marks]

a.i.

     A1A1

[2 marks]

a.ii.

use of area =  1 2 a b sin C      M1

1 2 × 1 × 2 × sin π 3 + 1 2 × 2 × 4 × sin π 3 + 1 2 × 4 × 8 × sin π 3       A1A1

Note: Award A1 for  C = π 3 , A1 for correct moduli.

= 21 3 2      AG

Note: Other methods of splitting the area may receive full marks.

[3 marks]

b.

1 2 × 2 0 × 2 1 × sin π n + 1 2 × 2 1 × 2 2 × sin π n + 1 2 × 2 2 × 2 3 × sin π n + + 1 2 × 2 n 1 × 2 n × sin π n       M1A1

Note: Award M1 for powers of 2, A1 for any correct expression including both the first and last term.

= sin π n × ( 2 0 + 2 2 + 2 4 + + 2 n 2 )

identifying a geometric series with common ratio 22(= 4)     (M1)A1

= 1 2 2 n 1 4 × sin π n      M1

Note: Award M1 for use of formula for sum of geometric series.

= 1 3 ( 4 n 1 ) sin π n      A1

[6 marks]

c.

Examiners report

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

Syllabus sections

Topic 1—Number and algebra » AHL 1.13—Polar and Euler form
Show 81 related questions
Topic 1—Number and algebra

View options