# Maple, anyone?

1. Mar 12, 2005

### juef

Hey all,

I'm having trouble setting initial conditions when solving differential equations in Maple. Here's the equation:

$$\theta(t)''+4\pi^2 sin(\theta(t))=0$$, with $$\theta(0)=A$$ and $$\theta'(0)=B$$ as initial conditions.

I'd like to solve it with a command like:
solution:=dsolve({diff(theta(t), t, t) + 4*Pi*sin(theta(t)=0, init_conds},theta(t),numeric,range=0..4);

with something like:
init_conds:={theta(0)=A, diff(theta, t)=B);

But it seems Maple doesn't like my way of doing things... I've searched the help file, but couldn't find one that suits my problem.

Anyone? Thank you!!

2. Mar 12, 2005

### Data

Try this:

dsol:=(A,B)->dsolve({(D@@2)(theta)(t)+4*Pi^2*sin(theta(t)), theta(0)=A, D(theta)(0)=B}, numeric);

then the command

dsol(a,b)(T);

will evaluate the solution with ICs A = a, B = b, at t = T.

3. Mar 13, 2005

### vladimir69

here is what i did
doesnt give u a nice solution but it works nonetheless
(student):
diff(theta(t),t,t)+4*Pi*Pi*sin(theta(t))=0;
dsolve({%,theta(0)=A,D(theta)(0)=B},theta(t));

perhaps if u plugged in some values instead of "A" and "B" it might give u something more exciting

4. Mar 13, 2005

### juef

Man, I didn't know about that D operator, the only thing I used was diff. Your help is extremely appreciated. Thanks a bunch both of you!! See my appreciation in the attachment!

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