Re: Assuming and Integrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg128328] Re: Assuming and Integrate*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Sun, 7 Oct 2012 01:31:55 -0400 (EDT)*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*: <20121006055312.C0D5B6908@smc.vnet.net>

How to treat exceptional cases, here m = n an integer, is always an issue with Integrate (and other operations). Here one would hope to see at least a ConditionalExpression for the general situation Element[{n,m}, Integers]. After all, such integrals are so common in Fourier analysis. Perhaps this should even be reported as a bug to Wolfram Research. On Oct 6, 2012, at 1:53 AM, hamiltoncycle at gmail.com wrote: > When I try the line below in Mathematica 8 I get the answer 0 which is what I expect when m and n are different but not when m=n. Can anyone explain how to do this correctly? > > Assuming[Element[{n, m}, Integers], Integrate[Sin[n*x]*Sin[m*x], {x, 0, Pi}]] > > When m=n we should get Pi/2, as in this case: > > Assuming[Element[n, Integers], Integrate[Sin[n*x]*Sin[n*x], {x, 0, Pi}]] > --- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**Assuming and Integrate***From:*hamiltoncycle@gmail.com