snow leopard
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In phase portraits I've seen saddle points sketched in two orientations: '+' and 'x'.

How do you know which orientation to sketch the saddle point?
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Farhan.Hanif93
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(Original post by snow leopard)
In phase portraits I've seen saddle points sketched in two orientations: '+' and 'x'.

How do you know which orientation to sketch the saddle point?
I assume this is in reference to a pair of equations of the form:

\begin{Bmatrix} \dot{x} = f(x,y) \\ \dot{y} = g(x,y)

You calculate the eigenvectors of the Jacobian matrix corresponding to the linearisation of your system of differential equations about the point of interest. Those will determine the directions in which the axes of your saddle point will (locally) be inclined.

Give an example if you'd like more of a hand.
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