diff(integrate(cos(k*x)*cos(n*x),x));



I got this result using trigsimp.
But I don't know how to get cos(k*x)*cos(n*x).
Can anyone tell me?

(C22) TRIGSIMP(DIFF(INTEGRATE(COS(k*x)*COS(n*x),x),x));

                        COS((n + k) x) + COS((n - k) x)
(D22)                   -------------------------------
                                       2

On Mon, Jan 13, 2003 at 07:00:44PM +0100, Khiraly Kalman wrote:
> Hi!
> diff(integrate(cos(k*x)*cos(n*x),x));
> 
> Why doesn't done the same resultat?:
> Theoretically diff(integrate(f(x)))=f(x)
> 
> But maxima doesn't.
> 
>  diff(integrate(cos(k*x)*cos(n*x),x))=cos(k*x)*cos(n*x)
> 
> Thanks   
> 
> 
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-- 
Wang Yin
DA Lab, Tsinghua University,
100084
Beijing China