Linear system with complex eigenvalues: are my eigenvectors correct?

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stunner5000pt
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For this linear system with complex eigenvalues
a) find the eigenvalues
b) determine whether the origin is a spiral source, sink or center
c) Determine the direction of oscillations, clockwise or anticlockwise

[tex]\frac{dY}{dt} = \left(\begin{array}{cc}0&2\\-2&0\end{array}\right) Y[/tex] with initial conditions [tex]Y_{0} = (1,0)[/tex]

i foudn the eigenvalues to be
[tex]\lambda = \pm i \sqrt{2}[/tex] which would make it a center
also the eigenvectors
[tex]\left(\begin{array}{cc}0&2\\-2&0\end{array}\right) \left(\begin{array}{cc}x\\y\end{array}\right) = \pm i \sqrt{2} \left(\begin{array}{cc}x\\y\end{array}\right)[/tex] i computed to be
[tex]V_{1} = \left(\begin{array}{cc}i\sqrt{2}\\1\end{array}\right)[/tex]
and [tex]V_{1} = -V_{2}[/tex]

i feel i made a mistake in finding the eigenvectors
also what would be the direction of the oscillations then?? Do i solve the Initial value problem to get hte direction of the oscillations??
 
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You have V1 correct but V2 is NOT -V1.
[tex]V_{2} = \left(\begin{array}{cc}-i\sqrt{2}\\1\end{array}\right)[/tex]

In order to determine the direction of rotation, look what happens to (1, 0):
dx/dt= 2y= 0 but dy/dt= -2 so the "motion" is downward and the rotation is clearly clockwise.
 
thank you very much :smile: didnt realize that the dx/dt and dy/dt were the directions of the vector. But what if the matrix was i nthe form
a b
c d then would i have to reduce this till i get zeroes in the 1x2 and 2x1 spots?