If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Unit 5: Complex numbers

900 possible mastery points

About this unit

Complex numbers are built on the idea that we can define the number i (called "the imaginary unit") to be the principal square root of -1, or a solution to the equation x²=-1. From this starting point evolves a rich and exciting world of the number system that encapsulates everything we have known before: integers, rational, and real numbers.
Level up on the above skills and collect up to 400 Mastery points
Level up on the above skills and collect up to 320 Mastery points
Up next for you:

Unit test

Level up on all the skills in this unit and collect up to 900 Mastery points!