[HP Prime] Using n-root symbol and exponent problem uklo Junior Member Posts: 12 Threads: 5 Joined: Oct 2013 11-09-2013, 01:32 PM Why is this happening? It is not the same? :( Les Koller Senior Member Posts: 253 Threads: 20 Joined: Jun 2012 11-09-2013, 03:25 PM Hmmm, that is strange. Hope someone figures it out. HP 50G gives same answer either way (the answer you have second). Richard Berler Member Posts: 109 Threads: 38 Joined: Dec 2012 11-09-2013, 05:28 PM Odd...I got the same result (top screen) on both Home and CAS regardless of maximum or none for auto simplification. The 2 results are correct...how does one get the simplified result for the 1st case? uklo Junior Member Posts: 12 Threads: 5 Joined: Oct 2013 11-09-2013, 07:04 PM I'm not sure if both answers are correct. I did it using 2 other CAS: wolfram alpha and Pocket CAS (for iOS) and i got the second result on both. I plot them and the result is a hyperbola, but the first result is only the positive side of that hyperbola... that's weird, obviously the second result is the correct one. I hope this get fixed soon *O* Terje Vallestad Junior Member Posts: 24 Threads: 2 Joined: Sep 2011 11-10-2013, 08:26 AM Quite interesting, but if you use the Sto command and store both expressions into F1 and F2 for plotting, both show the second answer 2/(6x-3). So presumably only the second answer is correct? Richard Berler Member Posts: 109 Threads: 38 Joined: Dec 2012 11-10-2013, 12:59 PM I was thinking that (x^(-a))*x^(+a)=x^0=1 which would produce the numerator of 2 in the example. Terje Vallestad Junior Member Posts: 24 Threads: 2 Joined: Sep 2011 11-10-2013, 02:10 PM Yes I believe (know) you are correct. I was more thinking of the anomaly that when the two expressions (that showed such different expressed results on the CAS screen) were stored into variables they both showed the latter more simplified result. Alberto Candel Member Posts: 72 Threads: 16 Joined: Sep 2013 11-11-2013, 01:39 AM I believe that for the HP Prime the nth root symbol (n odd) of a real number x and the power x^(1/n) are different things. The power x^(1/n) is computed as exp((1/n) LN(x)). If x is negative, then the HP Prime computes LN(x) as the complex number LN(|x|)+ i*pi (principal determination of the logarithm). For the nth root symbol of x, the HP Prime returns x^(1/n) if x is positive and -|x|^(1/n) is x is negative. So the results differ by the multiplicative constant exp(i*pi/n). This should not be a difference for the computation shown because taking LN makes the difference into an additive constant which then should disappear when taking the derivative. I suspect that the HP prime uses different algorithms to simplify each expression. By the way, the HP50g interprets the nth root of x and the power x^(1/n) the same way, as exp((1/n) LN(x)) with LN(x)=LN(|x|)+i*pi if x is negative. « Next Oldest | Next Newest »

 Possibly Related Threads... Thread Author Replies Views Last Post Prime Emulator Connection Problem John Colvin 3 457 12-14-2013, 11:00 PM Last Post: Han HP Prime: problem with the memory of calculator during the debug process? Carlos CM (Mexico) 7 646 12-06-2013, 12:34 PM Last Post: Carlos CM (Mexico) Problem with debug HP prime program, somebody help me? Carlos CM (Mexico) 6 601 12-05-2013, 03:07 PM Last Post: Carlos CM (Mexico) [HP Prime] CAS font problem Thomas Ritschel 1 251 11-08-2013, 09:43 AM Last Post: Javier Goizueta HP Prime - Variable problem bluesun08 12 774 11-07-2013, 11:34 AM Last Post: bluesun08 PRIME Spreadsheet RPN Problem Dougggg 5 461 10-24-2013, 11:46 PM Last Post: Han HP-80 CHS Exponent Curiosity Max Stone 4 434 10-22-2013, 02:39 PM Last Post: Max Stone Prime pinch problem David Hayden 4 380 10-09-2013, 11:22 AM Last Post: Tim Wessman Unexpected problem with the real Prime Javier Goizueta 4 402 10-08-2013, 01:00 PM Last Post: Marcus von Cube, Germany Cubic root (-8) = 2 ? Gilles Carpentier 37 1,942 08-12-2013, 10:26 PM Last Post: jep2276

Forum Jump: