How do I express complex numbers in the form reiθ?

How do I express complex numbers in the form re? Complex numbers have a general form of a+ib, i being imaginary. To answer this it is best shown on an argand diagram. Plot your complex number, then the angle at which the complex expression is plotted is your theta and its distance is "r". 

Example 3+4i

Using pythagaros we find "r": (32+42)1/2=5

Using trigonometry we find "θ": tan-1(4/3)=0.927 Rad

Therefore 3+4i is represented as 5e0.927i

KL
Answered by Kishen L. Further Mathematics tutor

44982 Views

See similar Further Mathematics A Level tutors

Related Further Mathematics A Level answers

All answers ▸

Using graphs, show how the Taylor expansion can be used to approximate a trigonometric function.


A particle is undergoing circular motion in a horizontal circle, that lies within the smooth surface of a hemispherical bowl of radius 4r. Find the distance OC (explained in diagram) if the angular acceleration of the particle is equal to root (3g/8r).


Find the square root of complex number 3 + 4i


a) Find the general solution to the differential equation: f(x)=y''-12y'-13y=8. b) Given that when x=0, y=0 and y'=1, find the particular solution to f(x).


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:

© 2025 by IXL Learning