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Questions on the use of numerical functions NIntegrate and NDSolve.

0 votes
1 answer
248 views

Why would NIntegrate give a negative value for this strictly-positive integrand?

NIntegrate[ Exp[Log[(a/3 - c/3) (a/3 - b/2 + c/6) (a/3 + b/2 + c/6)] + 1/2 (-((15 a^2)/4) - (15 b^2)/4 - (5 c^2)/4)] Boole[ c >= b >= 0] Boole[c >= a], {a, -Infinity, Infinity}, {b, 0, I …
Allure's user avatar
  • 625
4 votes
1 answer
124 views

Same integral, NIntegrate gives two different results?

They're the same integral - the bottom integral is simply the top one split up using the identity $\log(xy) = \log(x) + \log(y)$. But the results aren't the same. Why? Code for top integral: NInte …
Allure's user avatar
  • 625
4 votes
2 answers
286 views

Why do I get "PrincipalValue cannot work with the specified exclusions" when feeding a list ... [closed]

I have the following test function which I want to evaluate at various points from $x=0$ to $5$: $f(x) = \int^{20}_{1}\frac{1}{x-y} dy$ There's clearly a singularity here in the integral at $x=y$, w …
Allure's user avatar
  • 625