Complex numbers- College Algebra
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Transcript of Complex numbers- College Algebra
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Lesson P.6 (pg:60)
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In the beginning there were counting numbers (Natural Numbers)
And then we needed Integers
1
2
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In the beginning there were counting numbers
And then we needed integers
1
2-1
-3
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In the beginning there were counting numbers
And then we needed integers
And rationals
1
2-1
-3
0.41
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In the beginning there were counting numbers
And then we needed integers
And rationals
And irrationals1
2-1
-3
0.41
2
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In the beginning there were counting numbers
And then we needed integers
And rationals
And irrationals
And reals1
2-1
-3
0.41
2
0
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1
2
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8
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By definition
Consider powers if i
10
21 1i i
2
3 2
4 2 2
5 4
1
1 1 1
1
...
i
i i i i
i i i
i i i i i
It's any number you can imagine
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7
6
5
4
3
2
i
i
i
i
i
i
ii
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7
6
5
4
3
22 11
i
i
i
i
i
i
ii
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7
6
5
4
3
22
111
1
11
i
i
i
i
iii
i
ii
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1
1
161284
151173
141062
13951
iiii
iiiii
iiii
iiiii
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Now we can handle quantities that occasionally show up in mathematical solutions
What about
16
1a a i a
49 18
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Combine real numbers with imaginary numbers◦ a + bi
Examples
17
Real partImaginary
part
3 4i
36
2i
4.5 2 6i
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We have always used them. 6 is not just 6 it is 6 + 0i. Complex numbers incorporate all numbers.
1
2-1
-3
0.41
2
3 + 4i2i
0
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A number such as 3i is a purely imaginary number
A number such as 6 is a purely real number
a + ib is the general form of a complex number
6 + 3i is a complex number
-2 + 7i is also a complex number
Note:
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If x + iy = 6 – 4i
then x = 6 and y = -4
The ‘real part’ of 6 – 4i is 6
The ‘imaginary part’ of 6 – 4i is -4
20
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3i = 0 + 3i
-7= -7 + 0i
0= 0 + 0i
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Write these complex numbers in standard form a + bi
1. 2.
3. 4.
22
9 75 16 7
5 144 100
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Complex numbers can be combined with ◦ Addition
◦ Subtraction
◦ Multiplication
◦ Division
23
3 8 2i i
9 12 7 15i i
2 4 4 3i i
3
5 2
i
i
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Example 1:
24
2 4 4 3i i
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Example 2:
25
3 8 2i i
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Example 3:
(Use FOIL method)
26
9 12 7 15i i
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We need to know Conjugate of a+bi= a-bi
(Conjugate of a complex number is obtained
by changing the sign of the imaginary part)
For example:
27
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28
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To solve
Multiply and divide by
its conjugate
29
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Qs. Simplify
The trick is to make the denominator real:
2
3 7i
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6. Simplify
The trick is to make the denominator real:
2
3 7i
2 3 7 2(3 7)
3 7 3 7 58
(3 7)
29
7 3
29
i i
i i
i
i
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Example 4:
Division technique◦ Multiply numerator and denominator by the
conjugate of the denominator
32
3
5 2
i
i
2
2
3 5 2
5 2 5 2
15 6
25 4
6 15 6 15
29 29 29
i i
i i
i i
i
ii
3
5 2
i
i
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1. Simplify4
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Evaluate : 3 4i i
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3. Simplify3 4i i
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6. Simplify2
3 7i
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)(23
2
1166
2
166
2
52366
0136.7 2
Conjugatessolutionscomplexix
x
x
x
xxSolve
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Use the correct principles to simplify the following:
39
3 121
4 81 4 81
2
3 144
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Lesson P.6
Page - 65
Exercises 1 – 32, 37, 38,
41, 42, 55-62
40