       Re: wrong result when computing a definite integral

• To: mathgroup at smc.vnet.net
• Subject: [mg129405] Re: wrong result when computing a definite integral
• From: Alex Krasnov <akrasnov at eecs.berkeley.edu>
• Date: Fri, 11 Jan 2013 22:22:44 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: l-mathgroup@wolfram.com
• Delivered-to: mathgroup-newout@smc.vnet.net
• Delivered-to: mathgroup-newsend@smc.vnet.net
• References: <20130111023916.C722668DD@smc.vnet.net>

```Integrate takes the integration variables in prefix order, so perhaps you
meant the following:

In:	Integrate[Exp[I*Sqrt*y], {y, -Pi, Pi}, {x, -2*Pi, 2*Pi}]
Out:	(8*Pi*Sin[Sqrt*Pi])/Sqrt

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%2C-2Pi%2C2Pi%7D%2C%7By%2C-Pi%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 y], {x, -2 Pi, 2 Pi}, {y, -Pi, Pi}] -> -((4 I (-1 + E^(2 I Sqrt Pi)) Pi)/Sqrt)
>
> from some trial and error it seems the result is also incorrect for non-integer factors in the exponential.
>

```

• Prev by Date: Re: Plotting objective function in FindMinimum
• Next by Date: Re: wrong result when computing a definite integral
• Previous by thread: wrong result when computing a definite integral
• Next by thread: Re: wrong result when computing a definite integral