Consider the system in R² given in polar coordinates by fr = r(1 — r²) 8 = 1. (a) Find all limit cycles and all equilibria. (b) Determine stability of all limit cycles and equilibria.
Given system of equations:
To find:
a) The limit cycles and all equilibria.
b) Stability of the limit cycle and all equilibria.
Solution process:
Limit cycle can be identified by solving the differential equations.
Stability of the limit cycles can be identified using the limit of solution on r approaches to infinity.
Equilibrium solutions can be identified by equating the derivative to zero.
Stability of the equilibria can be identified by finding the eigenvalues of the Jacobian matrix.
Concept used:
If the eigenvalues are negative, then the node is stable node at equilibria, otherwise unstable.
If the eigenvalues are alternative with one as negative, then the node as saddle points.
If the eigenvalues are non-negative and Lyopunov function exists, then the point is stable node. Otherwise it is unstable.
Lyopunov function exists only if there exists a finite number of limit cycles.
Integration formula:
Here, is an integrating constant.
Differentiation formula:
, for any real n.
Logarithmic law:
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