CODEWITHSUNDEEP
wolfram-mathematica
Adeel Ahmad
Adeel Ahmad

Reputation: 3

Indefinite integral not evaluated in Mathematica

I have an Indefinite integral integral:

Rm = 50; d = 3; W = 1.2;
f = 1/(1 - R^2/Rm^2)
A = W*(d - 1 + X)/d*R^(X - 1) - R*f - (1 - d)/R;
B=W/d*R^X + 1;
Integrate[A/B, R]

Mathematica evaluate the above mentioned integral only for X = 0, 1 and 2 but not for the other non-integers values. (Note: for my problem X belong to [0,2].) I have also evaluated this integral in Maple 11. Maple give results for all values of X. But I want these results in Mathematica.

Thanks,

Upvotes: 0

Views: 221

Answers (1)

agentp
agentp

Reputation: 6999

The problem is the 'inexact' floating point value of W=1.2. If you use W=12/10 you get a result. Note in this case you actually get a faster/cleaner result if you leave all the numeric values out except for X until after integration:

 Clear[d,W,Rm,X];
 f = 1/(1 - R^2/Rm^2);
 A = W*(d - 1 + X)/d*R^(X - 1) - R*f - (1 - d)/R;
 B = W/d*R^X + 1;
 Block[{X = 3}, 
     Simplify[Integrate[A/B, R] /. {d -> 3, W -> 1.2, Rm -> 50}]]

1.0627 ArcTan[0.57735 - 0.850791 R] - 0.05 ArcTanh[0.02 R] + 2. Log[R] + 0.614458 Log[1.44225 + 1.06266 R] - 5.*10^-7 Log[-2500. + R^2] - 0.307229 Log[2.08008 - 1.53262 R + 1.12924 R^2] + 1. Log[3. + 1.2 R^3]

Aside you really should avoid starting your own variable names with caps to avoid conflicts with built in symbols.

Upvotes: 1

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