 Infinite sum wrong result. Bug in Giac? - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: Infinite sum wrong result. Bug in Giac? (/thread-2723.html) Infinite sum wrong result. Bug in Giac? - danielmewes - 12-29-2014 01:55 AM 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+%28%28%281%2Bi%29%2F2%29^k%29%2C+k%3D1+to+infinity Trying a few finite upper boundaries on the Prime suggests that Wolfram Alpha is correct, and Giac/Prime are wrong. RE: Infinite sum wrong result. Bug in Giac? - danielmewes - 12-29-2014 01:58 AM Versions: HP Prime 2014 12 3 (6975) xcas 1.1.3 RE: Infinite sum wrong result. Bug in Giac? - Helge Gabert - 12-29-2014 02:49 AM Confirmed. And, by the same token, sum from k=1 to infinity (((1-i)/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 (((-1-i)/2)^k) should return -2/5-i/5, but the Prime returns -2/5 only.] RE: Infinite sum wrong result. Bug in Giac? - parisse - 12-29-2014 09:20 AM Fixed in source, thanks. RE: Infinite sum wrong result. Bug in Giac? - danielmewes - 12-30-2014 04:07 AM Thanks for the super quick fix Bernard! Let's see when we get it for the Prime...