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Differential EquationsMediumNonlinear Systems & Linearization

Nonlinear Systems & Linearization · Medium problem

The system x′=x−3y−x(x2+y2),  y′=3x+y−y(x2+y2)x' = x - 3y - x(x^2 + y^2),\; y' = 3x + y - y(x^2 + y^2) has a limit cycle. Find its period.