[CAS] sum
12-17-2014, 11:21 AM
Post: #7
 Snorre Member Posts: 101 Joined: Dec 2013
RE: [CAS] sum
Hello,

As was already pointed out, you should do ∑(approx(sin(n)/n,...) instead of approx(∑(sin(n)/n,...)) to avoid forcing the CAS to build really long symbolic terms.

But what makes me wonder is why the "undef" result.
For example: sum(1/k,k=1..n) returns "undef" if there aren't any assumptions made about n ("euler_gamma+Psi(n+1)" if assume(n>0)).
On the other side: sum(1/|k|,k=1..n) returns just the term I've entered (regardless of assumptions about n).

Despite both sums should return the same, I'm fine with the latter since it tells me the CAS wasn't able to find a closed form solution.
But the first result "undef" seems wrong to me (I'd expect it for such cases like 0/0 etc.) and hard to track if the sum is part of a bigger expression.
(I've set automatic simplification to "None")
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 Messages In This Thread [CAS] sum - compsystems - 12-17-2014, 03:04 AM RE: [CAS] sum - Helge Gabert - 12-17-2014, 03:20 AM RE: [CAS] sum - compsystems - 12-17-2014, 03:35 AM RE: [CAS] sum - Helge Gabert - 12-17-2014, 03:41 AM RE: [CAS] sum - Han - 12-17-2014, 03:43 AM RE: [CAS] sum - parisse - 12-17-2014, 08:11 AM RE: [CAS] sum - Snorre - 12-17-2014 11:21 AM

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