Eigenvalue method for homogeneous eq's

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SUMMARY

The discussion centers on the calculation of eigenvectors and eigenvalues in the context of homogeneous equations. The eigenvalue used is λ = 3 - 4i, leading to the eigenvector V = [1, i]. The participant derived equations x1(t) and x2(t) as x1(t) = e^(3t)[C1 cos(4t) - C2 sin(4t)] and x2(t) = e^(3t)[C1 cos(4t) - C2 sin(4t)], noting a discrepancy with the book's use of "+" instead of "-". The participant seeks clarification on the sign error in their equations.

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  • Understanding of eigenvalues and eigenvectors
  • Familiarity with homogeneous differential equations
  • Knowledge of complex numbers and their properties
  • Proficiency in matrix operations and substitutions
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  • Review the process of calculating eigenvectors for complex eigenvalues
  • Study the derivation of solutions for homogeneous differential equations
  • Examine the impact of sign changes in trigonometric functions within solutions
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Students and professionals in mathematics, particularly those studying linear algebra and differential equations, as well as educators seeking to clarify concepts related to eigenvalues and eigenvectors.

cue928
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I am working on a problem and before I post the remaining questions on it, I want to be sure I calculated the eigenvector correctly. The eigenvalue I used was lambda = 3-4i.

[tex] \begin{bmatrix} 3-lambda & -4\\ 4 & 3-lambda\end{bmatrix}[/tex]
After substituting, the eigenvector I came up with is V = [1 i]
 
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cue928 said:
I am working on a problem and before I post the remaining questions on it, I want to be sure I calculated the eigenvector correctly. The eigenvalue I used was lambda = 3-4i.

[tex] \begin{bmatrix} 3-lambda & -4\\ 4 & 3-lambda\end{bmatrix}[/tex]
After substituting, the eigenvector I came up with is V = [1 i]

Fine so far.
 
Okay, so I have V = [1 i] and lambda = 3-4i
I came up with the following eq's that differed from the book only in the signs I placed in quotation marks...
x1(t) = e^3t[C1 cos(4t) "-" C2 sin(4t)]
x2(t) = e^3t[C1 cos(4t) "-" C2 sin(4t)]

In both cases, the book uses a "+" instead. But, I can't figure out where I dropped the sign.
 

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