College Algebra / Unit 4 Alg 181 short lesson, about 20 seconds
The Imaginary Unit
Captions available
The idea
The imaginary unit i is defined as the square root of −1, so that i² = −1; i is the principal, positive root.
In practice
No real number squares to a negative, so i lives off the real line — a new number admitted under the old rules.
Where people slip
i is a number, not a variable.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
- Nothing. This is a starting point.
Unlocks
- Nothing yet depends on this.
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