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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92613] Re: [mg92588] Why is Mathematica assuming k==l and how do I make it
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Wed, 8 Oct 2008 06:25:34 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

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 <aaronfude 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



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