View Full Version : Partial Differential Equation
EDerkatch
Nov21-06, 07:25 AM
x(δu/δx)-(1/2)y(δu/δy)=0
By first looking for a separable solution of the form u(x, y)=X(x)Y(y), find the general solution of the equation given above.
Determine the u(x,y) which satisfies the boundary condition u(1,y)=1+siny
For the separable form I have u(x, y)=A(x^c)(y^2c), could someone please show me how to do the rest of it.
Thank you.
arildno
Nov21-06, 07:28 AM
Write sin(y) as a power series.
arildno
Nov21-06, 07:36 AM
Each choice of c gives you a solution of your diff.eq.
Since your diff.eq is linear, a sum of such solutions is also a solution of your diff.eq.
EDerkatch
Nov21-06, 07:49 AM
How do I get from u(x, y)=A(x^c)(y^2c) to the general solution?
Thank you.
arildno
Nov21-06, 08:04 AM
All right:
A series solution of your diff.eq is:
u(x,y)=\sum_{n=1}^{\infty}A_{n}x^{c_{n}}y^{2c_{n}} ,
whereby follows:
u(1,y)=\sum_{n=1}^{\infty}A_{n}y^{2c_{n}}
and A_{n},c_{n} are constants.
Now, how can you fit this expression for u(1,y) to the given boundary condition?
EDerkatch
Nov21-06, 10:22 AM
All right:
A series solution of your diff.eq is:
u(x,y)=\sum_{n=1}^{\infty}A_{n}x^{c_{n}}y^{2c_{n}} ,
whereby follows:
u(1,y)=\sum_{n=1}^{\infty}A_{n}y^{2c_{n}}
and A_{n},c_{n} are constants.
Now, how can you fit this expression for u(1,y) to the given boundary condition?
Please go on...
arildno
Nov21-06, 10:23 AM
Well, use my first hint in post 2.
EDerkatch
Nov21-06, 04:06 PM
Well, use my first hint in post 2.
Ok if you could please show me the COMPLETE working I would really appreciate it... Thank you.
EDerkatch
Nov21-06, 04:07 PM
Well, use my first hint in post 2.
Ok if you could please show me the COMPLETE working I would really appreciate it... Thank you.
arildno
Nov21-06, 04:20 PM
Do you know what a power series is? :confused:
EDerkatch
Nov21-06, 04:40 PM
Do you know what a power series is? :confused:
Yes lol, I just can't do this question, could you please show me the working for it... In fact can you do it yourself?
HallsofIvy
Nov21-06, 07:32 PM
If you are not capable of doing basic algebra, you should not be attempting partial differential equations!
(Yes, I can do it myself! That's not really the point is it? You have been told exactly HOW to solve your equation, yet you have not even TRIED to apply what you have been told.)
arildno
Nov22-06, 06:14 AM
Yes lol, I just can't do this question, could you please show me the working for it... In fact can you do it yourself?
That's it. I'm out of here. It is long since I've met a more ungrateful and lazy f*ckhead on PF as you.
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