Re: Question
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg458] Re: [mg450] Question
- From: bob Hanlon <hanlon at pafosu2.hq.af.mil>
- Date: Sun, 12 Feb 1995 22:09:41
> Message-Id: <9502080805.AA13790 at christensen.cybernetics.net.> > Date: Tue, 7 Feb 1995 12:08:01 -0500 > To: mathgroup at christensen.cybernetics.net > From: deburm at tiac.net (David E. Burmaster) > Subject: [mg450] Question > > +++++++++++++++ > > Dear MathGroup: > > Any suggestions on how to integrate this function from zero to +Infinity?? > > a, b, and c are positive constants > > a is approx 0.75 > b is approx 4 > c is approx 0.1 > > Here is the function that I wish to integrate > > S = Exp[ -1 ( a (1 - Exp[ -b t]) + c t ) ] > > ++++++ > > NIntegrate should do the job, but I am hoping to find a closed-form solution > I couldn't find any simple way of doing it in Mathematica, so I looked it up in a table. Bob Hanlon hanlon at pafosu2.hq.af.mil ____________________ Clear[f, g]; f[a_Real, b_Real, c_Real] := NIntegrate[Exp[-1 (a (1 - Exp[-b t]) + c t)], {t, 0, Infinity}]; g[a_Real, b_Real, c_Real /; c/b > 0] := Exp[-a] (-a)^(-c/b) Gamma[c/b, 0, -a]/b // Chop (* Gradshteyn & Ryzhik, 4th Edition, 1965, Eqn. 3.331.1 *) Table[{{a, b, c}, f[a, b, c], g[a, b, c]}, {a, 0.5, 1.0, 0.25}, {b, 3.5, 4.5, 0.5}, {c, 0.08, 0.12, 0.02}] {{{{{0.5, 3.5, 0.08}, 7.67837, 7.67837}, {{0.5, 3.5, 0.1}, 6.16154, 6.16154}, {{0.5, 3.5, 0.12}, 5.15016, 5.15016}}, {{{0.5, 4., 0.08}, 7.6665, 7.6665}, {{0.5, 4., 0.1}, 6.14978, 6.14978}, {{0.5, 4., 0.12}, 5.13852, 5.13852}}, {{{0.5, 4.5, 0.08}, 7.65722, 7.65722}, {{0.5, 4.5, 0.1}, 6.14059, 6.14059}, {{0.5, 4.5, 0.12}, 5.1294, 5.1294}}}, {{{{0.75, 3.5, 0.08}, 6.02595, 6.02595}, {{0.75, 3.5, 0.1}, 4.84442, 4.84442}, {{0.75, 3.5, 0.12}, 4.05654, 4.05654}}, {{{0.75, 4., 0.08}, 6.01104, 6.01104}, {{0.75, 4., 0.1}, 4.82966, 4.82966}, {{0.75, 4., 0.12}, 4.04192, 4.04192}}, {{{0.75, 4.5, 0.08}, 5.9994, 5.9994}, {{0.75, 4.5, 0.1}, 4.81811, 4.81811}, {{0.75, 4.5, 0.12}, 4.03047, 4.03047}}}, {{{{1., 3.5, 0.08}, 4.73432, 4.73432}, {{1., 3.5, 0.1}, 3.81396, 3.81396}, {{1., 3.5, 0.12}, 3.20018, 3.20018}}, {{{1., 4., 0.08}, 4.71763, 4.71763}, {{1., 4., 0.1}, 3.79743, 3.79743}, {{1., 4., 0.12}, 3.18379, 3.18379}}, {{{1., 4.5, 0.08}, 4.70459, 4.70459}, {{1., 4.5, 0.1}, 3.78449, 3.78449}, {{1., 4.5, 0.12}, 3.17096, 3.17096}}}}