1. January 17, 2012 At the end of today, you will be able to understand how to use complex numbers.
Warm-up: Correct HW 5.6b
HW 5.9: Pg. 274 #18-29 all, 83, 84
Quiz Friday!

2. Lesson 5.9a Complex Numbers
What is a complex number?
A complex number is a combination of real and imaginary numbers
What is an imaginary number?
Anything with an “i”
It is in the form a + bi
a is the “real” part
bi is the “imaginary” part
What can we do with complex #s?
- Add or subtract - Multiply Divide

3. Using Imaginary Numbers
In Real Number Land, you cannot have an negative in an even root. But in Imaginary Number Land, YOU CAN! *The Law in Imaginary Land: Example 1: Simplify Rewrite using i

4. Practice rewriting radicals using i.

5. Powers of i Powers of i i1 = i2 = i3 = i4 = i5 = i6 = i7 = i8 =
The pattern repeats after every multiple of 4.
Is there a pattern? -1
How can you use the pattern to find i17? -i
i17 = i 1 i
Use the pattern to find i43?
i42 = -1 -1 -i 1