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Re: Help with differential equation

• To: mathgroup at smc.vnet.net
• Subject: [mg112257] Re: Help with differential equation
• From: "Nasser M. Abbasi" <nma at 12000.org>
• Date: Tue, 7 Sep 2010 02:00:44 -0400 (EDT)
• References: <i627tc$b9$1@smc.vnet.net>
• Reply-to: nma at 12000.org

On 9/6/2010 1:14 AM, mathpavi wrote:
> Dear experts,
> I tried solving  the following differential equation using DSolve:
>
> y' ' [x]+a( y' [x] ) = b( cos[y] )
>
> But I got error message which asked me to provide proper arguments for
> cos..
> So I changed cos[y] to cos[kx] and obtained solution...
> However, I have to solve the equation by keeping cos[y] in order to
> obtain a solution of relevance to my work.
> Please help.
> praveen
>

it is Cos not cos, (Mathemaica is case sensitive) and also you need to 
write y[x] not just y inside the Cos and need to use == not =


Try:

de = y''[x]+ a y'[x] == b Cos[ y[x] ]

DSolve[de, y[x], x]


But this is non-linear ode, may be try a numerical solution?

--Nasser