Infinite sum wrong result. Bug in Giac?

12292014, 01:55 AM
Post: #1




Infinite sum wrong result. Bug in Giac?
Hi all,
I was reading this bug report for the 50g http://bugs.hpcalc.org/show_bug.cgi?id=238 and entered the same sum into the Prime for testing: sum from k=1 to infinity (((1+i)/2)^k) the Prime gives me 0 as the result. CAS mode, Settings: Exact on, Complex off (turning it on doesn't change the result), Use sqrt on, Use i on. I can also reproduce this in Giac/Xcas: `sum(((1+i)/2)^k, k=1...+infinity)` gives me 0 as well. In contrast, WolframAlpha says the result is i http://www.wolframalpha.com/input/?i=sum...o+infinity Trying a few finite upper boundaries on the Prime suggests that Wolfram Alpha is correct, and Giac/Prime are wrong. 

12292014, 01:58 AM
Post: #2




RE: Infinite sum wrong result. Bug in Giac?
Versions:
HP Prime 2014 12 3 (6975) xcas 1.1.3 

12292014, 02:49 AM
(This post was last modified: 12292014 03:40 AM by Helge Gabert.)
Post: #3




RE: Infinite sum wrong result. Bug in Giac?
Confirmed.
And, by the same token, sum from k=1 to infinity (((1i)/2)^k) should return i, but the Prime also thinks it is zero. [Edit: Also checked sum from k=1 to infinity (((1+i)/2)^k) should return 2/5+i/5, but the Prime returns 2/5. Ditto sum from k=1 to infinity (((1i)/2)^k) should return 2/5i/5, but the Prime returns 2/5 only.] 

12292014, 09:20 AM
Post: #4




RE: Infinite sum wrong result. Bug in Giac?
Fixed in source, thanks.


12302014, 04:07 AM
Post: #5




RE: Infinite sum wrong result. Bug in Giac?
Thanks for the super quick fix Bernard!
Let's see when we get it for the Prime... 

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