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

Posted 1 year ago
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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}] 
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Posted 1 year ago
 It may be that the integral does not exist. If so, you can still obtain numerical results: int[Delta_, J_] := NIntegrate[ 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