Find the four complex roots of the equation z^4 = 8(3^0.5+i) in the form z = re^(i*theta)

We know that z=re^(itheta) from the definition of the exponential form of a complex number. Hence it follows that: z^4=(re^(itheta))^4=r^4e^(4itheta) We can find z^4 by converting 8(3^0.5+i) (cartesian form) into exponential form by finding the modulus and argument of this: (I will do the working of this question on the whiteboard when asked) z^4=16e^i(π/6 + 2Kπ) , where K is any integer. We have needed to add 2Kπ to account for the arbitrary number of rotations; any integer K can vary the argument by 2π K times however since this is a full rotation this argument will still represent the same complex number. We know that z^4=(re^(itheta))^4=r^4e^(4itheta) hence we can compare coefficients: r^4=16 implies r=2 z^4=(re^(itheta))^4=r^4e^(4itheta) 4theta = π/6+2Kπ impllies theta = π/24 + 0.5Kπ We are not given an interval for the argument so we assume the standard interval (-π,π) and find all arguments of each root within this interval by considering all the possible values of K: k=0 case theta=1/24π k=1 case theta=13/24π k=-1 case theta =-11/24π k=-2 case theta = -23/24π Hence we can conclude the four complex roots in exponential form are: 2e^(i1/24π), 2e^(i13/24π), 2e^(i-11/24π), 2e^(i*-23/24π)

GG
Answered by George G. Further Mathematics tutor

6267 Views

See similar Further Mathematics A Level tutors

Related Further Mathematics A Level answers

All answers ▸

The plane Π contains the points (1, 2, 3), (0, 1, 2) and (2, 3, 0). What is the vector equation of the plane? and what is the cartesian equation of the plane?


Solve the inequality x/(x+2) ≤ 4/(x-3) for x ≠ -2 or 3


How do I find the inverse of a 3x3 matrix?


Using z=cos(θ)+isin(θ), find expressions for z^n-1/z^n and z^n+1/z^n


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