### Author Topic: Lecture Notes 7 -- Ex 3-4  (Read 2994 times)

#### Shu Wang

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##### Lecture Notes 7 -- Ex 3-4
« on: October 14, 2012, 01:25:44 AM »
sorry for stealing the post; I've got a question regarding to Example 3 and 4 on Lecture 7.
How do you turn the Robin boundary conditions to a function of psi and phi?

#### Victor Ivrii

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##### Re: Lecture Notes 7 -- Ex 3-4
« Reply #1 on: October 14, 2012, 04:29:34 AM »
sorry for stealing the post; I've got a question regarding to Example 3 and 4 on Lecture 7.
How do you turn the Robin boundary conditions to a function of psi and phi?

It is not stealing but hijacking. Just plug $u=\phi(x+ct)+\psi (x-ct)$ into b.c. and you get a mixture of $\psi'(-ct)$, $\psi(-ct)$ and $\phi'(x+ct)$, $\phi(ct)$. But you know $\phi(ct)$ so you get 1-st order ODE for $\psi$.

#### Shu Wang

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##### Re: Lecture Notes 7 -- Ex 3-4
« Reply #2 on: October 14, 2012, 01:31:28 PM »
rofl, thanks alot.