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### Messages - Rong Wei

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31
##### HA5 / Re: HA5-P6
« on: October 17, 2015, 06:26:23 PM »

32
##### HA5 / Re: HA5-P3
« on: October 17, 2015, 04:18:42 PM »
and for question b, it should be x - ct instead of x - vt; otherwise, we couldn't have the solution.

33
##### HA4 / Re: HA4-P2
« on: October 17, 2015, 03:14:54 PM »
professor, I don't understand why Ï•(0) = 0 only when without jumps?

34
##### HA5 / HA5-P3
« on: October 17, 2015, 02:55:31 PM »
previous post should be HA5 - P1, sorry about the typo!

35
##### HA4 / Re: HA4-P2
« on: October 17, 2015, 12:10:11 AM »
the answer for âˆ’c2t<x<0, Yeming Wen add one constant - 1 / 2  Ï•(0) in the bracket [].
let k be the constant multiplying Ï•(c1/c2(x+c2t)),
plug x = 0 in U | t = 0 by the initial condition, then we will have U(0,0) = Ï•(0)
so this constant should be Ï•(0) (1 / k - 1) in the bracket [].

for 0<x<c1t, same steps used in calculate the constant in the brackets [].

36
##### HA4 / Re: Quiz 3 Answers
« on: October 16, 2015, 11:53:51 PM »
because plug x = 0 in U|t = 0 = Ï•(x), we will have
U|t = 0, x = 0 = Ï•(0)
(1)

and plug x = 0, t = 0 in u(x,t)=4/3 Ï•(12x+t), we will have

U(0,0) = 4/3 Ï•(0)
(2)

conclude (1) and (2), we will have the answer by Fei Fan Wu

37
##### HA5 / Re: HA4-P1
« on: October 16, 2015, 08:58:54 PM »
I'm not sure

38
##### HA5 / HA5-P1
« on: October 16, 2015, 08:30:07 PM »

39
##### HA4 / Re: HA4-P1
« on: October 14, 2015, 06:17:43 PM »
Now I understand its the part we discussed should be c integrate Xï¼ˆxï¼‰ from t - x/c to 0

40
##### HA4 / Re: HA4-P1
« on: October 14, 2015, 12:51:25 AM »
My solution is Ï•(x+ct)âˆ’1/câˆ«ctâˆ’x0X(tâˆ’xc)+Ï•(ctâˆ’x)for for {0<x<ct},  Because the boundary condition is Ux|x=0=Ï‡(t), so we should integral Ï‡(t). I plug in the derivative of U respect to x, and I got this answer, may be I'm wrong? I'm not sure,

41
##### HA2 / Re: HA2-P5
« on: October 01, 2015, 01:43:07 PM »
you are so rightï¼ see you in class!

42
##### HA2 / Re: HA2-P5
« on: September 30, 2015, 12:09:10 AM »
For 5b, I know derivative of arcsin(x) is 1/(1-x^2)^(1/2), can I use this to calculate the integral ? sorry about my typo, I haven't download matlab yet, I will download it~

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