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HP Forum Archive 21

 Simplify with sci/eng on hp 50gMessage #1 Posted by Juraj O. on 6 Nov 2012, 4:38 a.m. When I change into engineering/scientific mode with a precision of e.g. 1 digit, '70E-9 *cos(0)' gets simplified into 1/e^16 (cas is set to exact). What is going on here?

 Re: Simplify with sci/eng on hp 50gMessage #2 Posted by Crawl on 6 Nov 2012, 5:37 p.m.,in response to message #1 by Juraj O. I am unable to reproduce your error. I get 7.0E-8 A couple of questions: -In the answer, is that e the normal (2.71828...) e? -Do you have E defined to be a variable with a value? -Can you explain *exactly* what you're doing? Example, I am in RPN mode, enter 70E-9 *cos(0) in single quotes, and hit EVAL (or simplify, whatever) and get 7.0E-8

 Re: Simplify with sci/eng on hp 50gMessage #3 Posted by Juraj O. on 6 Nov 2012, 6:37 p.m.,in response to message #2 by Crawl Set mode to engineering with precision 1, cas mode exact. Open equation editor, enter cos(0) * 0.01 (another example). Select whole expression and simplify it, or close the equation editor and invoke SIMPLIFY (EVAL does not exhibit this behaviour). It gets simplified to 1/e^5 (yes, that's e, the exponential function).

 Re: Simplify with sci/eng on hp 50gMessage #4 Posted by Juraj O. on 6 Nov 2012, 6:50 p.m.,in response to message #2 by Crawl I have made a recording of this in the emulator: http://www.mediafire.com/?9cnml3z1c3yvhw8

 Re: Simplify with sci/eng on hp 50gMessage #5 Posted by Bart (UK) on 7 Nov 2012, 6:15 a.m.,in response to message #1 by Juraj O. Hi Juraj,I confirm I get the same strange result when using SIMPLIFY and low display digits in Exact Mode. This seems to be a problem with version 2.15 of the calculator firmware. In version 2.09 it will request Approx. mode and display the correct answer.To others,Just entering the equation with EVAL it seems it always gets the right answer, irrespective of display digits setting.To reproduce the error:Have version 2.15 and set display to either FIX 1, SCI 1 or ENG 1Enter the equation in Equation Writer, select it completely and use SIMPorenter the equation on the command line '70E-9·COS(0)' go to CONVERT -> REWRITE -> SIMPLIFYEDIT:Further to the above: it seems also to be a problem with the 50g association of integers and exact mode, and floating numbers and approx. mode.Enter the equation as:(70/1000000000)*COS(0)and it will simplify it correctly.Thus the v. 2.09 response is correct to request Approx. Mode because of the 70E-9. It does not request it when 70/1000000000 is entered. The 50g is wrong by just giving an answer that is incorrect. Something broke here between 2.09 & 2.15. Edited: 7 Nov 2012, 6:48 a.m.

 Re: Simplify with sci/eng on hp 50gMessage #6 Posted by Juraj O. on 7 Nov 2012, 10:56 a.m.,in response to message #5 by Bart (UK) In approx mode, 1•0.01 gets simplified right into 6.7E-3. This is really dangerous! How the hell did not anyone discover this earlier? That was on my 3rd or 4th day of owning a 50g.... Edited: 7 Nov 2012, 10:59 a.m.

 Re: Simplify with sci/eng on hp 50gMessage #7 Posted by Gilles Carpentier on 7 Nov 2012, 11:25 a.m.,in response to message #6 by Juraj O. How do you do ? In RPN mode I get the right answer

 Re: Simplify with sci/eng on hp 50gMessage #8 Posted by Bart (UK) on 7 Nov 2012, 11:39 a.m.,in response to message #7 by Gilles Carpentier Quote: How do you do ? In RPN mode I get the right answer Hi Gilles, v2.09 does get the right answer, but v2.15 gets the answer that Juraj noted. (we are talking about SIMPLIFY command with low digit ENG/SCI/FIX mode). Edited: 7 Nov 2012, 11:52 a.m.

 Re: Simplify with sci/eng on hp 50gMessage #9 Posted by Bart (UK) on 7 Nov 2012, 11:44 a.m.,in response to message #6 by Juraj O. Quote: How the hell did not anyone discover this earlier? That was on my 3rd or 4th day of owning a 50g.... I guess most users like lots of numbers and do not normally use the SIMPLIFY function with such low digit requirements. Quote: In approx mode, 1•0.01 gets simplified right into 6.7E-3. It still seems to try and use the Exact techniques (in Exact mode it gives 1/e^5, which = 6.7E-3 with "-> NUM" in FIX 1). When entering it as '1·(1/100)' the correct answer is produced.It seems to try and find the nearest answer representable with e. I tried several flag settings, but nothing seems to help. Perhaps others have better ideas. As I said, it seems something here broke between v2.09 and 2.15. Edited: 7 Nov 2012, 12:06 p.m.

 Re: Simplify with sci/eng on hp 50gMessage #10 Posted by Crawl on 8 Nov 2012, 10:34 a.m.,in response to message #9 by Bart (UK) Interesting. I tested this on a emulator, though, which would have been an older version. I left my physical HP50g at home, so I'll have to check this on that later.

 Re: Simplify with sci/eng on hp 50gMessage #11 Posted by Crawl on 16 Nov 2012, 7:24 p.m.,in response to message #10 by Crawl Quote: Interesting. I tested this on a emulator, though, which would have been an older version. I left my physical HP50g at home, so I'll have to check this on that later. It looks like my physical calculator does have this issue. Maybe I should try to install an older version?

 Re: Simplify with sci/eng on hp 50gMessage #12 Posted by Han on 8 Nov 2012, 6:26 p.m.,in response to message #5 by Bart (UK) I can also confirm this behavior on the HP50G ROM 2.15 Han

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