Oswego City School District
Regents Exam Prep Center: Cyclic Nature of the Powers of "I"
Students learn two easy methods to simplify "i" with any exponent. The practice page has several problems that include explanations. The teacher resource page has two possible activities for helping students understand the concept.
Oswego City School District
Regents Exam Prep Center: Simplifying Square Roots With Negative Numbers
This tutorial and practice shows how to simplify radicals even with a negative number. Features include a teacher page that has a Bingo game to teach the concept.
Wolfram Research
Wolfram Math World: Imaginary Number
Contains a brief definition of an imaginary number. Includes special links and topic search engine.