For each of the following systems, find the fixed points, classify them, sketch the neighboring trajectories, and try to fill in the rest of the phase portrait. 6.3.1 dot{x} = x - y, dot{y} = x^2 - 4 6.3.2 dot{x} = sin y, dot{y} = x - x^3
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I assume the systems are: 6.3.1: $\dot{x} = X - Y$, $\dot{y} = X - 4$ 6.3.2: $\dot{x} = \sin y$, $\dot{y} = x$ Now, let's find the fixed points and classify them for each system. 6.3.1: Show more…
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Consider the system { dot{x} = x, dot{y} = y - y^2. Sketch the phase portrait by completing the following steps. First, find and classify the fixed points. Then sketch the nullclines (that is, a set of points in the phase space where dot{x} = 0 and the set of points where dot{y} = 0). Finally, fill in representative trajectories using the classification of the fixed points.
Adi S.
Sri K.
6.3.9 (15 pts) Consider the system ẋ = y^3 - 4x, ẏ = y^3 - y - 3x. (a) Find all the fixed points and classify them. (b) Show that the line x = y is invariant, i.e., any trajectory that starts on it stays on it. (c) Show that |x(t) - y(t)| → 0 as t → ∞ for all other trajectories. (Hint: Form a differential equation for x - y.) (d) Sketch the phase portrait. (e) If you have access to a computer, plot an accurate phase portrait on the square domain -20 < x, y < 20. (To avoid numerical instability, you'll need to use a fairly small step size, because of the strong cubic nonlinearity.) Notice the trajectories seem to approach a certain curve as t → -∞; can you explain this behavior intuitively, and perhaps find an approximate equation for this curve?
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