Casio FX602P vs fx4000P, different results

10272021, 04:23 PM
Post: #1




Casio FX602P vs fx4000P, different results
Hi!
i tried a simple calculation on 2 of my CASIO, the FX602P and the fx4000P. i did just simply sqrt 2, and then ^2 of the result on both. FX602P : sqrt 2 = 1.414213562 this result ^2 gives 2. fx4000P: sqrt 2 = 1.414213562 this result ^2 gives 1.999999999 Anyone know why the FX602P comes up with the correct answer 2, and the fx4000P not? Maybe simple to explain, but i cant figure it out. 

10272021, 07:33 PM
Post: #2




RE: Casio FX602P vs fx4000P, different results
Both calculators evaluate results to 12 significant figures: \(\sqrt{2}\approx 1.414\,213\,562\,37\). Squaring this number gives 2, to 10 significant figures. This is what is displayed on the FX602P.
However, pressing the EXE key on the FX4000P rounds the result to 10 significant figures: \(\sqrt{2}\approx 1.414\,213\,562\). Squaring this rounded number gives \(1.999\,999\,999\), to 10 significant figures. The rounding happens, I guess, because registers on the FX4000P only store 10 significant figures. Pressing EXE stores the displayed number into the Ans register, hence the rounding. There is no Ans register on the FX602P, and in any case the FX602P's registers store all 12 digits of a calculated result. Typing \((\sqrt{2})^2\) EXE on the FX4000P gives an answer of 2, as the rounding doesn't occur until the calculation is complete. Incidentally, the answer on the FX602P is not exactly correct. Squaring \(1.414\,213\,562\,37\) gives \(1.999\,999\,999\,99\), rounded to 12 significant figures. The FX602P rounds the answer to 2, exactly. Quite a lot of Casio calculators do this  personally, I disapprove! Nigel (UK) 

10272021, 08:21 PM
Post: #3




RE: Casio FX602P vs fx4000P, different results
wow, that was a great explanation!
I had no idea of this. So, the old FX602P handles this much better than the newer fx4000P then. 

10272021, 08:42 PM
Post: #4




RE: Casio FX602P vs fx4000P, different results
Thank you! I agree: in this respect, the FX602P is definitely the better of the two. Still, the FX4000P wins on builtin functions!
Nigel (UK) 

10282021, 07:32 AM
Post: #5




RE: Casio FX602P vs fx4000P, different results  
10282021, 08:18 AM
Post: #6




RE: Casio FX602P vs fx4000P, different results
It should be noted that the "correct" answer of 2 isn't.
Rounding to different numbers of digits is evil and misleading. Pauli 

10282021, 02:55 PM
(This post was last modified: 10282021 02:55 PM by Maximilian Hohmann.)
Post: #7




RE: Casio FX602P vs fx4000P, different results
Hello!
Could it be, that the FX602P (don't have one in my collection (yet) so can't try it out myself) has a display formating function similar to "DSP" on the HPs? When I perform the operation above on an HP67 (for example) then I will get 2.00 in the default DSP 2 setting wheras it shows 1.999999999 in DSP 9. And I agree with those who have written above that 2 is not the correct answer. If you calculate the trajectory of a Saturn probe with a calculator (or rather a computer) that comes up with 2 for the square of 1.414213562 then your probe is going to miss Saturn by a very wide margin... Regards Max 

10282021, 05:32 PM
Post: #8




RE: Casio FX602P vs fx4000P, different results
Thank you all for your input, i learn new things of calculators (casio) here!
So, i comes down to WHEN the casio do the rounding of digits if i get it right? But, if so, how can fx4000P, calculate (sqrt 2)^2 to 2? I just tried it, and i get the result 2. Isnt the rounding in play here, or has the calculator a table of the right answers in rom? 

10282021, 05:33 PM
Post: #9




RE: Casio FX602P vs fx4000P, different results
This post provides some history of why HP chose not to round off the answers on their calculators.
https://www.hpmuseum.org/forum/thread17...49274.html 

10282021, 05:57 PM
Post: #10




RE: Casio FX602P vs fx4000P, different results
(10282021 05:33 PM)Steve Simpkin Wrote: This post provides some history of why HP chose not to round off the answers on their calculators. Interesting reading, and examples! But i'm a bit confused, 1/3+1/3+1/3 gives 1.0 on fx4000P. Is that bad or good? 

10282021, 06:16 PM
Post: #11




RE: Casio FX602P vs fx4000P, different results  
10282021, 07:01 PM
Post: #12




RE: Casio FX602P vs fx4000P, different results
(10282021 06:16 PM)Maximilian Hohmann Wrote: Hello! Actually, the 34S returns E16, which is more correct than 1. After you do 3 [1/x] [Enter] [Enter] + +, the display shows 1.000000000 (assuming fix 9), but if you then do 1 [], you'll see the actual result revealed here; it was just hiding due to your display setting. Bob Prosperi 

10282021, 09:28 PM
Post: #13




RE: Casio FX602P vs fx4000P, different results
(10282021 05:32 PM)Dan C Wrote: Thank you all for your input, i learn new things of calculators (casio) here! If you enter \((\sqrt{2})^21\) followed by EXE the FX4000P returns \(1\times10^{11}\), which shows that \((\sqrt{2})^2\) is being correctly evaluated as \(1.999\,999\,999\,99\) to 12 significant figures. However, entering \((\sqrt{2})^2\) followed by EXE returns 2 exactly, because of the rounding to 10 significant figures that happens when EXE is pressed. (Interestingly, the TI68 calculator allows the user to choose whether pressing ENTER rounds to 10 digits, or whether the full 13digit precision is retained.) Nigel (UK) 

11162021, 08:00 PM
(This post was last modified: 11162021 08:03 PM by Dan C.)
Post: #14




RE: Casio FX602P vs fx4000P, different results
Wow, i really like the knowledge of calculators on this forum!
Things like if the calculator use 10 or 12 digits, and when and where it does it. I have now used the fx4000P a little bit more, making some small programs, and using BASEn with logical operations etc., and i say as many before me, this must be one of the best calculators ever. beside of the HP's then . 

11192021, 08:48 PM
Post: #15




RE: Casio FX602P vs fx4000P, different results
(10272021 04:23 PM)Dan C Wrote: i tried a simple calculation on 2 of my CASIO, the FX602P and the fx4000P.I just tried it on my fx 4000 and it also gave 2 ( sqrt 2 EXE , ^2 EXE) I don't have a real 602P to test with. A 602P emulator on my phone also gave 2 but that does not say anything. 

11192021, 11:46 PM
Post: #16




RE: Casio FX602P vs fx4000P, different results  
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