lesson 79 – exponential forms of complex numbers hl2 math - santowski
TRANSCRIPT
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LESSON 79 – EXPONENTIAL FORMS OF COMPLEX NUMBERS
HL2 Math - Santowski
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Opening Exercise #1
List the first 8 terms of the Taylor series for (i) ex, (ii) sin(x) and (iii) cos(x)
HENCE, write the first 8 terms for the Taylor series for eθ
HENCE, write the first 8 terms for the Taylor series for eiθ. Simply your expression.
What do you notice?
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Opening Exercise #2
If y(θ) = cos(θ) + i sin(θ), determine dy/dθ
Simplify your expression and what do you notice?
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EXPONENTIAL FORMEXPONENTIAL FORM
( ) cos( ) sin( )y x x i x
or
( ) cos( ) sin( )z i
dy
dx sin cosx i x ( sin cos )i i x x
iy
Which function does this?dy
kydx
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EXPONENTIAL FORMEXPONENTIAL FORM
kxy Ae
So (not proof but good enough!)
(cos sin ) iz r i re
If you find this incredible or bizarre, it means youare paying attention.
Substituting gives “Euler’s jewel”:
1 0ie which connects, simply, the 5 mostimportant numbers in mathematics.
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Forms of Complex Numbers
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Conversion Examples
Convert the following complex numbers to all 3 forms:
€
( ) a 4−4i
( ) b −2 2 +3 2i
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Example #1 - Solution
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Example #2 - Solution
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Further Practice
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Further Practice - Answers
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Example 5
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Example 5 - Solutions
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Verifying Rules …..
If
Use the exponential form of complex numbers to determine:
€
z1 =r1ei 1 andz2 =r2e
i2
€
( ) a z1 ×z2
( ) bz1z2
( ) c1z1
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Example 6
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Example 6 - Solutions
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And as for powers …..
Use your knowledge of exponent laws to simplify:
€
( ) a 5x3k( )
4
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And as for powers …..
Use your knowledge of exponent laws to simplify:
€
( ) a 5x3k( )
4
( ) b 5e3 i( )
4
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So .. Thus …..
€
zn =(rcis)n =rncis(n)zn =(rei )n =rnein
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And de Moivres Theorem ….. Use the exponential form to:
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de Moivres Theorem
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Famous Equations …..
Show that
€
ei +1 =0
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Challenge Q
Show that
€
(3+4i)(6+7 i) =−10.3−21.4i