The Museum of HP Calculators

HP Forum Archive 13

 Gamma function differences?Message #1 Posted by Nelson M. Sicuro (Brazil) on 30 Aug 2003, 11:40 p.m. Hi to all! I was just playing with my hp-42S and my newly arrived (and fixed!) HP-11C, and I found this difference: In the Gamma function (in HP-11C shared with factorial [n!]) I found these results: HP-11C: n = 68.5, result = 2.056343638e97 HP-42S: n = 68.5, result = 3.0019615151e95 HP-11C: n = 67.5, result = 3.00196151e95 HP-42S: n = 67.5, result = 4.44735039275e93 HP-11C: n = 66.5, result = 4.447350392e93 Commodore SR4190: n = 68.5, result = 3.00196151995e95 Commodore SR4190: n = 67.5, result = 4.44735039501e93 I'm just curious (as I don't have the HP-11C user's manual): the argument for Gamma function in the HP-11C is added by 1 internally? Regards, Nelson

 Re: Gamma function differences?Message #2 Posted by Brandon Del Bel on 31 Aug 2003, 1:21 a.m.,in response to message #1 by Nelson M. Sicuro (Brazil) Dude, gamma(x)=(x-1)! To calculate gamma(68.5) on your 11c, you need calculate the factiorial of 67.5 to get 3.001961515*10^95 (which is what you got for for your "n=67.5" except for the last decimal; I multiplied the result of 67.5! by 1e-95 to display all the digits.) On a side note, the results of your 42s match my 48gx and 49g. I hope this clarifies the discrepancy. Sincerely, Brandon

 Re: Gamma function differences?Message #3 Posted by Nelson M. Sicuro (Brazil) on 31 Aug 2003, 2:08 a.m.,in response to message #2 by Brandon Del Bel This is because the gamma function in HP-11C is "hidden" in the factorial function? The use of the same key is clever, but as I said I don't have the manual, and I really forgot about the gamma(n) = (n-1)! equivalence... Thanks! Best regards, Nelson

 Re: Gamma function differences?Message #4 Posted by Ellis Easley on 31 Aug 2003, 4:24 a.m.,in response to message #3 by Nelson M. Sicuro (Brazil) Viktor Toth has a good discussion of the gamma function at rskey.org:

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