# Coupled differential equation using NDSolve

I am using mathematica to solve a coupled differential equation using NDSOlve and stuck with it. Could you please help me out to figure out the solution. My problem is

$$A[\omega]:= A''[r]+\frac{f'[r]}{f[r]}A'[r]+\frac{\omega^2}{f[r]^2}-\frac{\mu^2}{f[r]}A[r]+\frac{\mu}{I \omega}S[r]=0$$, $$S''[r] + \frac{f'[r]}{f[r]}S'[r] + \frac{\omega^2}{f[r]^2}S[r]- \frac{1}{U[r]^2} h[r]=0$$ and $$S[r]=\frac{I \omega}{f[r]}(\mu A[r]+h'[r]-h[r])$$

• "stuck with it" - can you show the code you used? Jul 19, 2016 at 6:03
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– user9660
Jul 19, 2016 at 6:13
• People here generally like users to post code as Mathematica code instead of images or TeX, so they can copy-paste it. It makes it convenient for them and more likely you will get someone to help you.
– user9660
Jul 19, 2016 at 6:13
• – user9660
Jul 19, 2016 at 6:13
• OP also has network issues... Jul 19, 2016 at 7:30

Too long for comment: There's a difference between equation == and setting a variable=. In the NDSolve[] you appear to be "setting" h[0]=1 You need to change this to an equation ==, then quit the kernel (so that h[0] is "unset", and try running the code again.

As you failed to provide the code I cannot check if this is sufficient to run the code smoothly.

I would also like to advise you that it is considered bad form to use single capital letter variables like A.

• Good eye, spotting = ... Jul 20, 2016 at 14:07