This lesson introduces the notion of imaginary numbers. Students are asked to recall that multiplying a number on the number line by -1 results in a 180 degree rotation about the origin. Using this logic, imaginary numbers are introduced as a 90 degree rotation about the origin.

It is then noted how imaginary numbers can help us to solve certain equations that we were not able to solve before. This leads to a connection between i and the square roots of negative numbers.

Finally, the operations of addition, subtraction, multiplication, and division are introduced for imaginary numbers.

This lesson is appropriate for Algebra 2, though it could also be used in an Honors Algebra 1 class or as a review in Precalculus.

A detailed answer key is included.

The topics covered include:
-Extending the Geometry of the Number Line
-Using Imaginary Numbers
-Square Roots of Negative Numbers
-Adding and Subtracting Pure Imaginary Numbers
-Multiplying Pure Imaginary Numbers
-Dividing Pure Imaginary Numbers
-Powers of i

In this product, you will find the following:
-Powerpoint Presentation (22 slides)
-Guided Notes (4 pages, a "filled in" copy is also included)
-Do Now Slips (4 slips on one page, answers included)
-Exit Ticket Slips (4 slips on one page, answers included)
-Homework Assignment (2 pages, a detailed answer key is included)

This lesson is part of a larger unit on Complex Numbers. The complete unit includes the following:
-Imaginary Numbers
-Complex Number Arithmetic
-Solutions to Quadratic Equations (coming soon!)
-Solutions to Higher-Order Polynomial Equations (coming soon!)
-The Fundamental Theorem of Algebra (coming soon!)