
Re: wrong result when computing a definite integral
Posted:
Jan 11, 2013 10:22 PM


Integrate takes the integration variables in prefix order, so perhaps you meant the following:
In: Integrate[Exp[I*Sqrt[3]*y], {y, Pi, Pi}, {x, 2*Pi, 2*Pi}] Out: (8*Pi*Sin[Sqrt[3]*Pi])/Sqrt[3]
Alex
On Thu, 10 Jan 2013, Dexter Filmore wrote:
> hi group, > > i run into this problem today when giving a bunch of easy integrals to mathematica. > here's a wolfram alpha link to the problem: > http://www.wolframalpha.com/input/?i=Integrate%5BExp%5BI+Sqrt%5B3%5Dy%5D%2C%7Bx%2C2Pi%2C2Pi%7D%2C%7By%2CPi%2CPi%7D%5D# > > the integrand does not depend on the 'x' variable, the inner integration should only result in a factor of 4Pi, and the correct result is a real number, yet the below integral gives a complex number which is far off from the correct value: > Integrate[Exp[I Sqrt[3] y], {x, 2 Pi, 2 Pi}, {y, Pi, Pi}] > ((4 I (1 + E^(2 I Sqrt[3] Pi)) Pi)/Sqrt[3]) > > from some trial and error it seems the result is also incorrect for noninteger factors in the exponential. >

