Answers>Maths>IB>Article

Finding complex numbers using DeMoivre's Theorem

Find the cube roots of 21/2cis(pi/4)
21/2cis(pi/4+ 2pi k), for every integer k
By DeMoivre:
21/2
1/3cis((pi/4+ 2pi k)/3)321/6cis(pi/12+ 2/3pi *k)
Taking k=0,1,2 gives the three cube roots:z1= 21/6cis(pi/12) (k=0)z2= 21/6cis(3pi/4) (k=1)z3= 21/6cis(17pi/12) (k=2)

LR
Answered by Lisa R. Maths tutor

3644 Views

See similar Maths IB tutors

Related Maths IB answers

All answers ▸

Let Sn be the sum of the first n terms of the arithmetic series 2 + 4 + 6 + ... i) Find S4


Take the square root of 2i


Show that the following system of equations has an infinite number of solutions. x+y+2z = -2; 3x-y+14z=6; x+2y=-5


Solve the equation 8^(x-1) = 6^(3x) . Express your answer in terms of ln 2 and ln3 .


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning