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Topics - yingxuanwang

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Test 1 / Test 1 coverage
« on: March 02, 2022, 07:50:06 PM »
Hi Prof. Ivrii!

I have seen that the announcement on Quercus test 1 page said we would have four question in the test, for main sitting, 1 for first order, 2 for wave, 3&4 for heat(one whole, one half). But the practice past test that you posted is not the same coverage as the announcement, the practice contains:1 for first order, 2 for whole wave, 3 for half wave, and 4 for whole heat. I am so confused and I have checked with Prof. Kennedy, he said the test format he received is the same as the practice, and I make sure with him I am asking about the main sitting. Since I mentioned the difference coverage between practice and announcement, he took a look at something, I think that was internal announcement for instructor maybe, and he told me the format is the same as practice.

So I just want to make sure that tomorrow main sitting, we will have Q1 for first order, Q2 for whole wave, Q3 for half wave and Q4 for whole heat, right?

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Test 1 / Test 1 Wave equation and Heat equation questions
« on: March 01, 2022, 07:36:06 AM »
Hi Prof. Ivrii!

I wonder if we need to compute all the integral out for the heat and wave equation during the test?

Like for heat equation question, during the quiz, I found the final graded point is for simplifying the heat fomula, so I wonder if we can get full marks during test if we just simplify the fomula and leave the inside integral calculations? (I know I have had a quiz that the question cannot be integrated by it is an error function, maybe this is why we only need to simplify the fomula and leave it there)

The same question to the wave equation questions, do we need to do all detail calculations or just plug in (maybe simplify) the fomula and annotate the interval clear?

Thx!

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Chapter 3 / C3.2/P4/Q10
« on: February 16, 2022, 09:32:47 PM »
Hi I have facing difficulty with solving the 10th part of the Problem 4 in Chapter 3.2

This equation is quite different from others in Problem 4, since I am really not sure with my solution, can anyone check for me? My friend said he will solve it in a different way and he thinks my solution is wrong but he did not actually solve it. I have attached the question and my solution. It is really near the quiz and I have struggled on this problem for two days, please help me!

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Chapter 4 / C3.2/P4/Q10
« on: February 16, 2022, 09:29:58 PM »
Hi I have facing difficulty with solving the 10th part of the Problem 4 in Chapter 3.2

This equation is quite different from others in Problem 4, since I am really not sure with my solution, can anyone check for me? My friend said he will solve it in a different way and he thinks my solution is wrong but he did not actually solve it. I have attached the question and my solution. It is really near the quiz and I have struggled on this problem for two days, please help me!

5
Chapter 2 / Lec5101 Question Mock Quiz 1
« on: September 19, 2020, 09:11:39 PM »
Hi, I have a question when I solve the general solution of ODE.
When I calculate the integral, should I add the absolute value to the result? (see the picture)
I am confused about this because I think the constant "C" can cancel the absolute value there.
Also, can anyone help me to check if my answer totally correct or anywhere I can improve?
Look forward to a kind reply.
Thanks a lot!

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Chapter 2 / LEC5101 Question
« on: September 19, 2020, 12:46:43 AM »
Hi, I have a question when I solve the first order equation.
I have found that sometimes to multiple a factor to the equation to construct a exact equation is much more convenient to use formula to solve it. But it is hard for me to find such a integral factor, is there any techniques to use this method? Or how can I know when I should use such method?
Thanks.

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