Values of some integrals



>>>>> "Richard" == Richard Fateman <fateman at cs.berkeley.edu> writes:

    Richard> in commercial macsyma
    Richard> After setting intanalysis:false,

What happens if intanalysis has the default value of true?

    Richard> and saying that k is an integer and positive,
    Richard> I got these answers...

    Richard> [(( - ((sqrt(3) * %i)/2) - (1/2)) * 2^((2 * %i + 4)/3) * G(((2 * %i +
    Richard> 4)/3))/3),
    Richard> ((2 * 2^(1/3) * (((sqrt(3) * %i)/2) - (1/2)) * G((1/3)))/9),
    Richard>  ((2 * %i)/3),

Assuming G here means the gamma function, then these 3 seem to be
wrong, based on the derivation in Wang's thesis, p 84-85.

Wang says integrate(x^m*exp(%i*k*x^n),x,0,inf) is

exp(signum(k)*%i*%pi*(m+1)/(2*n))*gamma(s/n/(abs(k))^s)

where s = (m+1)/n.  I've gone over the derivation, and it looks
right. 

I'm surprised that Mathematica says the integrals don't converge.

    Richard> integrate(((x^k * log(x))/(x + 3)),x,0,inf)]

Wang says for k /= 0 and -1 < k < 1, this integral converges and can
be expressed in terms of the beta function and its derivatives.  I
haven't examined that yet.

Thanks, everyone, who evaluated the integrals for me,

Ray