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[Solved] Help for calculating triple definite integral, please.

Posted 1 year ago
2 Replies
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Hello everybody. I cannot calculate following problem. My software in my PC evaluates very long, but answer is not exist. Please, help me to calculate this problem:

Integrate[Sqrt[(2*Delta*J*(3 - Cos[Pi*x] - Cos[Pi*y] - Cos[Pi*z]) + J^2*(3 - Cos[Pi*x] - Cos[Pi*y] - Cos[Pi*z])^2)],{x,0,1},{y,0,1},{z,0,1}]
2 Replies
Posted 1 year ago

It may be that the integral does not exist. If so, you can still obtain numerical results:

int[Delta_, J_] := 
  Sqrt[(2*Delta*J*(3 - Cos[Pi*x] - Cos[Pi*y] - Cos[Pi*z]) + 
     J^2*(3 - Cos[Pi*x] - Cos[Pi*y] - Cos[Pi*z])^2)], {x, 0, 1}, {y, 
   0, 1}, {z, 0, 1}]

int[1, 1]

(* 3.853312214951417` *)

I used your code as written, but it is usually best to begin user-defined variables in lower case to prevent colliding with reserved words.

Kind regards, David

Thank you a lot. It succesfully work.

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