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[{ amplist[i1]= Read[StringJoin[jproc,"/",QCD[i1],"diagrams.amp"]], ileng[i1] = Length[amplist[i1]], Do[{ Print["Processing amp[",i1,",",i2,"]"], If[i1===2,{amp[i1,i2] = amplist[i1][[i2]][[3]]}, {amp[i1,i2] = amplist[i1][[i2]][[2]] }], ---------------------------------- and so on. What does amp[i1,i2] = amplist[i1] [[i2]] [[3]] 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.