Re: newbie: diff equation

• To: mathgroup at smc.vnet.net
• Subject: [mg96913] Re: [mg96886] newbie: diff equation
• From: "Ned Lieb" <okty.gy.ned at gmail.com>
• Date: Fri, 27 Feb 2009 06:12:03 -0500 (EST)
• References: <200902261301.IAA26650@smc.vnet.net>

```You have to use two equals signs instead of one when inputting a
differential equation.

-----Original Message-----
From: Mike [mailto:atkins1976 at yahoo.com]
Sent: Thursday, February 26, 2009 8:01 AM
To: mathgroup at smc.vnet.net
Subject: [mg96913] [mg96886] newbie: diff equation

My problem is very simple, I'm sure someone can help me out quickly. I am
trying to solve some systems of differential equations a bit like a particle
in a box (QM) so I started with this basic problem which I know how to solve
just to make sure I am entering everything ok, but I can't even get it to
work.

I want to solve f''[x]= - m^2 f[x]

with f[0] = 0 and f[Pi] = 0

this is obviously only solvable with the condition on m being integer but if
I do DSolve on the above with the boundary conditions I just get f=0. How
can I get mathematica to solve this and give me the conditions on m? I need
to solve much more general problems of this type. I hope someone can help.
Many thanks

```

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