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MAT244--2020F
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Chapter 2
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Lecture 0201 question
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Topic: Lecture 0201 question (Read 5799 times)
Suheng Yao
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Lecture 0201 question
«
on:
September 15, 2020, 12:24:18 PM »
This is the last question from yesterday's lecture 0201 section. I still don't understand why there is a negative sign on the right side of the equation?
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Victor Ivrii
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Re: Lecture 0201 question
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Reply #1 on:
September 15, 2020, 01:11:04 PM »
Indeed, there should be no $-$ on the right, unless I change $b-y$ to $y-b$ (which I intended to to but doid not). I updated handout, it is just a single place as on the next frame everything is right.
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Suheng Yao
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Re: Lecture 0201 question
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Reply #2 on:
September 15, 2020, 02:23:46 PM »
Thanks, prof. Also, on the next slide, I feel confused about why does f(x) have a single minimum at x=a and have equilibrium at x=a and y=b? I really don't get the idea here.
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Victor Ivrii
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Re: Lecture 0201 question
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Reply #3 on:
September 16, 2020, 03:47:54 AM »
You can investigate $f(x)$ as in Calculus I.
Also because $x=x(t)$ and $y=y(t)$ and $x=a,y=b$ is a constant solution (equilibrium). Look at the picture on the next slide. We excluded $t$ from our analysis but it does not mean that it had gone
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Jianfeng Huang
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Re: Lecture 0201 question
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Reply #4 on:
September 16, 2020, 11:20:50 AM »
I was also wondering how to extent the concept of direction field in this case, as both x and y are functions of t. Why the direction field shows the relationship between x and y? Is it because equations do not include t explicitly, and theoretically we can have 3-dimensional direction field?
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Victor Ivrii
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Re: Lecture 0201 question
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Reply #5 on:
September 17, 2020, 12:34:30 PM »
We use $x$ and $y$ because we can exclude $t$ but neither $x$ nor $y$
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Toronto Math Forum
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MAT244--2020F
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MAT244--Lectures & Home Assignments
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Chapter 2
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Lecture 0201 question