       Re: Why is Mathematica assuming k==l and how do I make it

• To: mathgroup at smc.vnet.net
• Subject: [mg92684] Re: Why is Mathematica assuming k==l and how do I make it
• From: mariam <mariamsaleh.khan at gmail.com>
• Date: Fri, 10 Oct 2008 04:36:06 -0400 (EDT)
• References: <gci2il\$td\$1@smc.vnet.net>

```On Oct 8, 12:38 pm, Bob Hanlon <hanl... at cox.net> wrote:
> Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi},
>  Assumptions -> {l == k, Element[{l, k}, Integers]}]
>
> Pi
>
> Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi},
>  Assumptions -> {l != k, Element[{l, k}, Integers]}]
>
> 0
>
> Assuming[{l == k, Element[{k, l}, Integers]},
>  Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi}]]
>
> Pi
>
> Assuming[{l != k, Element[{k, l}, Integers]},
>  Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi}]]
>
> 0
>
> Bob Hanlon
>
> ---- Aaron Fude <aaronf... at gmail.com> wrote:
>
> =============
> As in
>
> Assuming[Element[{k, l}, Integers] ,
>  Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi}]]
>
> I get 0 whereas the answer is Pi if k=l;
>
> Thanks!
>
> Aaron
>
> --
>
> Bob Hanlon

hi all,
i found your group via web-search.
i am new to mathematica and learning about some codes needed in my
projects.
i want to know that:
1)

Do[{
ileng[i1] = Length[amplist[i1]],

Do[{
Print["Processing amp[",i1,",",i2,"]"],
If[i1===2,{amp[i1,i2] = amplist[i1][[i2]][]}, {amp[i1,i2] =
amplist[i1][[i2]][]
}],
---------------------------------- and so on.
What does amp[i1,i2] = amplist[i1] [[i2]] [] mean? I mean any
f[i.j]=g[i] [[j]] [[k]]
I am confused about the double-brackets used  [[----]].

2) in another expression,
itwo = StringPosition[jproc,"2"][[1,1]]

what for [[ x, y]] is used?

I'll be very grateful for your help.

```

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