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### Topics - Qingyang Wei

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##### MAT244--Lectures & Home Assignments / How to draw phase portraits by hand effectively?
« on: December 06, 2018, 01:44:44 PM »
The only method of drawing phase portrait that I am aware of is to evaluate each particular solutions of the system at a large amount of points, and "connect the dots" to produce a trajectory for the solution. But that seems to be very time consuming. Is there any more efficient way to draw this by hand?

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##### MAT244--Lectures & Home Assignments / Term Test 2 Question 1 Solve Integral
« on: December 05, 2018, 04:39:52 PM »
For question 1 a) of Term Test 2, i.e. Solve equation $y'' + 4y = 2\tan (t)$, how do you solve the integral to arrive at the particular solution of the equation? I see the solution to the question being posted in the Term test section of the forum but I am not sure how the particular solution $$y_p(t)=-\cos 2t(t-\sin (t)\cos (t))+\sin 2t(\log (\cos (t)) - 1/2 \cos 2t)$$ is calculated, specifically, how the integral is solved to arrive at this answer.

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