2. In this course you mainly work with matrices that have real eigenvalues. But, what about the matrices that do not have only real eigenvalues? Is benefiting from eigenvalues and eigenvectors limited only to the matrices with real eigenvalues? Of course not. One may think working with complex numbers is difficult, however, utilizing complex numbers in many engineering problems simplifies the problem-solving process and gives us better insight into the problem itself. One simple example here cab be a rotation matrix. a. You know a 2D rotation matrix is cos e - sin 0 R that rotates the input vector x to sin 0 Cos O the vector Rx that is rotated version of vector x in 0 degrees counter-clockwise. We know that there is not a general real vector (real numbers), that maps Rx in the same direction of x. Because the characteristic polynomial of this matrix is cos 8 – A - sin 0 (cos 0 – 1)? + sin? 0 = X² – (2 cos 0)A +1= 0 %3D sin 0 cos 0 – A

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ChapterP: Prerequisites: Fundamental Concepts Of Algebra
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Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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2. In this course you mainly work with matrices that
have real eigenvalues. But, what about the matrices that
do not have only real eigenvalues? Is benefiting from
eigenvalues and eigenvectors limited only to the matrices
with real eigenvalues? Of course not. One may think
working with complex numbers is difficult, however,
utilizing complex numbers in many engineering problems
simplifies the problem-solving process and gives us better
insight into the problem itself. One simple example here
cab be a rotation matrix.
a. You know a 2D rotation matrix is
Cos O
– sin 0
R
sin 0
that rotates the input vector x to
Cos O
the vector Rx that is rotated version of vector x in 0
degrees counter-clockwise. We know that there is not a
general real vector (real numbers), that maps Rx in the
same direction of x. Because the characteristic
polynomial of this matrix is
- sin 0
cos 8 – A
cos 8 – A
(cos 0 – 1)2 + sin? 0 = x² – (2 cos 0)A+1=0
sin 0
Using algebra find the complex roots of the above
second-degree characteristic polynomial. To do so you
only need one trigonometric identity that is
sin? 0+ cos? 0 = 1.
b. Draw the locus of the eigenvalues you found in par'
1
in a complex plane. Indicate the location of roots for
0 = 30°, 45°, 90°. For which angles of 0 the eigenvalues
of the rotation matrix are real (the imaginary part is zero)?
Imaginarr
Transcribed Image Text:2. In this course you mainly work with matrices that have real eigenvalues. But, what about the matrices that do not have only real eigenvalues? Is benefiting from eigenvalues and eigenvectors limited only to the matrices with real eigenvalues? Of course not. One may think working with complex numbers is difficult, however, utilizing complex numbers in many engineering problems simplifies the problem-solving process and gives us better insight into the problem itself. One simple example here cab be a rotation matrix. a. You know a 2D rotation matrix is Cos O – sin 0 R sin 0 that rotates the input vector x to Cos O the vector Rx that is rotated version of vector x in 0 degrees counter-clockwise. We know that there is not a general real vector (real numbers), that maps Rx in the same direction of x. Because the characteristic polynomial of this matrix is - sin 0 cos 8 – A cos 8 – A (cos 0 – 1)2 + sin? 0 = x² – (2 cos 0)A+1=0 sin 0 Using algebra find the complex roots of the above second-degree characteristic polynomial. To do so you only need one trigonometric identity that is sin? 0+ cos? 0 = 1. b. Draw the locus of the eigenvalues you found in par' 1 in a complex plane. Indicate the location of roots for 0 = 30°, 45°, 90°. For which angles of 0 the eigenvalues of the rotation matrix are real (the imaginary part is zero)? Imaginarr
b. Draw the locus of the eigenvalues you found in part (a)
in a complex plane. Indicate the location of roots for
0 = 30°, 45°, 90° . For which angles of 0 the eigenvalues
of the rotation matrix are real (the imaginary part is zero)?
Imaginary
+i
Real
-1
C. Having the eigenvalues A1 and d2, find the complex
eigenvectors of the rotation matrix. Note that the vector
a
where a and B are complex numbers and
cos 0 – Ai
- sin 0
+B
Cos -
is an
sin 0
eigenvector for the eigenvalue of d;. Do eigenvectors of
the rotation matrix depend on the angle of rotation 0?
Transcribed Image Text:b. Draw the locus of the eigenvalues you found in part (a) in a complex plane. Indicate the location of roots for 0 = 30°, 45°, 90° . For which angles of 0 the eigenvalues of the rotation matrix are real (the imaginary part is zero)? Imaginary +i Real -1 C. Having the eigenvalues A1 and d2, find the complex eigenvectors of the rotation matrix. Note that the vector a where a and B are complex numbers and cos 0 – Ai - sin 0 +B Cos - is an sin 0 eigenvector for the eigenvalue of d;. Do eigenvectors of the rotation matrix depend on the angle of rotation 0?
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