Putting Casio fx991CW in perspective.

09202023, 07:07 AM
(This post was last modified: 12062023 08:16 AM by Matt Agajanian.)
Post: #1




Putting Casio fx991CW in perspective.
Hi all.
Call it what you will (blunder, disappointment, several steps backward, a flop, woefully inadequate, etc). Perhaps even to put it on par with the first & second editions of the 115ES let alone the 991ES editions, the CW falls short. Rather than use it as a paperweight, do you see the CW having any merits, applications, benefits? 

09202023, 03:36 PM
Post: #2




RE: Putting Casio fx991CW in perspective.
I do like that it uses 22 or 23 digits internally, produces exact fractions, pi multiples or fractions more often than other machines. When integrating near a discontinuity/vertical asymptote, one can integrate using a lower or upper limit 1*10^17 or 18 from the vertical asymptote and get a very accurate result. From a statistics point of view, retention of data when changing modes or powering off is very welcome.


09232023, 09:46 AM
(This post was last modified: 09232023 10:25 PM by carey.)
Post: #3




RE: Putting Casio fx991CW in perspective.
(09202023 07:07 AM)Matt Agajanian Wrote: Hi all. Here's a novel 991CW application: manual iteration to solve a transcendental equation using the 991CW's composite functions. The simple looking transcendental equation, e^x = x, is unsolvable in closed form (try it!). While easy to solve using a graphical calculator by plotting both the LHS and RHS and finding their intersection, equations such as this can also be solved by iteration, e.g., selecting a value for x, calculating e^x (which becomes the new value of x), rinse and repeat, with the values, if plotted, forming a cobweb plot. An iterative solution can be found using a spreadsheet like Excel or Google Sheets that permits circular references by selecting the iteration option and limiting the number of iterations (to prevent infinite loops). However, I've not found a calculator spreadsheet (including the 991CW spreadsheet) that allows circular references. On the 991CW one can use manual iteration via composite functions to work around the circular reference issue, and without a spreadsheet, as follows: 1) From Home, highlight Calculate, click EXE and click Function. 2) Highlight Define f(x), enter e^x, and click EXE. 3) Click Function, highlight Define g(x), click EXE, click x, and click EXE. 4) Click Variable, highlight x, enter 0.5 as an initial guess, click EXE. 5) Click Home, highlight Calculate, click EXE, click Function, highlight f(x) and complete "f(" by clicking "x" and entering ")" to get "f(x)" and select EXE. The first iterate 0.6065306597 is displayed. To manually obtain subsequent iterates, the steps are simply as follows. 6) Click Variable, highlight x, click EXE, highlight STORE, click EXE, and the first iterate becomes the new value of x. 7) Click EXE again to update the value of f(x) and obtain the 2nd iterate: 0.5452392119 8) Repeat steps 6 and 7 to obtain the remaining iterates. The first 12 iterates (sufficient to achieve convergence to within 0.001) are as follows (if no transcription errors). 1) 0.6065306597 2) 0.5452392119 3) 0.5797030949 4) 0.5600646279 5) 0.571172149 6) 0.564862947 7) 0.5684380476 8) 0.5664094527 9) 0.5675596343 10) 0.5669072129 11) 0.567277196 12) 0.5670673519 Wolfram Alpha gives the solution as 0.567143. 

09232023, 02:20 PM
Post: #4




RE: Putting Casio fx991CW in perspective.
A small modification of procedure written above
7) Click EXE again to update the value of f(x) and obtain the 2nd iterate: 0.5452392119 8) recall f() and insert ans, so you get f(ans) and press OK or EXE several times the final result is 0,567143xxxx 

09232023, 02:55 PM
Post: #5




RE: Putting Casio fx991CW in perspective.
(09232023 02:20 PM)klesl Wrote: A small modification of procedure written above That's a huge improvement, requiring only repeated EXE presses to obtain the next iterate! Thank you for suggesting it! 

09232023, 05:19 PM
(This post was last modified: 09232023 05:52 PM by Csaba Tizedes.)
Post: #6




RE: Putting Casio fx991CW in perspective.
MoHPC don't like Youtube shorts....
The link: https://www.youtube.com/shorts/1R3IMq227dM https://www.youtube.com/shorts/1R3IMq227dM 

09232023, 05:21 PM
(This post was last modified: 09232023 05:54 PM by Csaba Tizedes.)
Post: #7




RE: Putting Casio fx991CW in perspective.
Same, without d/dx()
https://www.youtube.com/shorts/8pGxTXSk40 https://www.youtube.com/shorts/8pGxTXSk40 

09232023, 06:40 PM
(This post was last modified: 09232023 06:50 PM by Eddie W. Shore.)
Post: #8




RE: Putting Casio fx991CW in perspective.
My favorite addition is the ability to access two functions f(x) and g(x) from anywhere.
The store button/function needs to come back. And the multistate colon. 

09232023, 06:45 PM
(This post was last modified: 09232023 06:51 PM by carey.)
Post: #9




RE: Putting Casio fx991CW in perspective.
(09232023 05:19 PM)Csaba Tizedes Wrote: MoHPC don't like Youtube shorts.... (09232023 05:21 PM)Csaba Tizedes Wrote: Same, without d/dx() Csaba, These videos are great  very nicely done! Thank you for sharing them! A quick question about Newton's method (shown in the videos). Newton's method has stood the test of time and has sound justification in Taylor series. Of the dozens* of other rootfinding methods that have been developed over the years, some general and some claiming to have advantages in special situations, are there one or two of these alternative methods that you have found particularly worthwhile to try in situations where Newton's method doesn't perform well? Thanks! * Alternative rootfinding methods include bisection, secant, regula falsi, Halley's, Broyden's, fixed point iteration, Steffenson's, Ridder's, Brent's, Muller's, Bairstow's, DurandKerner, and more...! 

09232023, 07:28 PM
Post: #10




RE: Putting Casio fx991CW in perspective.  
09242023, 12:41 AM
(This post was last modified: 09242023 07:27 AM by carey.)
Post: #11




RE: Putting Casio fx991CW in perspective.
(09232023 02:20 PM)klesl Wrote: A small modification of procedure written above After playing around with your great suggestion a little more, the entire procedure can be streamlined to avoid even using the x variable. Instead, after f(x) and g(x) functions are created, the initial guess (0.5) is entered in the Calculate screen so Ans becomes the initial guess. After that, your suggestion to create f(Ans) and repeatedly press EXE, gives each iterate. The entire streamlined procedure is as follows: 1) From Home, highlight Calculate, click EXE and click Function. 2) Highlight Define f(x), enter e^x, and click EXE. 3) Click Function, highlight Define g(x), click EXE, click x, and click EXE. 4) Enter 0.5, then click EXE. 5) Click Function, highlight f(x) and complete "f(" by clicking Ans and entering ")" to get "f(Ans)", select EXE and the first iterate 0.6065306597 is displayed. 6) To manually obtain subsequent iterates, click EXE repeatedly. 

09242023, 05:38 AM
Post: #12




RE: Putting Casio fx991CW in perspective.
(09232023 06:45 PM)carey Wrote: These videos are great  very nicely done! Thank you for sharing them! Thank you, unfortunately my (spoken and written) English really terrible, so you can enjoy them in Hungarian, if you check these: CASIO fx991CEX  a leghatékonyabb Classwiz Akcióban  CASIO fx991CEX  the most powerful Classwiz in ACTION: https://www.youtube.com/playlist?list=PL...ons3wS2cef Or these: CASIO Classwiz (fx991EX, 991DEX, 991CEX, fx92+ Spéciale Collége or *ANY* models): https://www.youtube.com/playlist?list=PL...qJUMxqyeP2 BTW I prefer the builtin solver, I have no other preferred method, in these videos I choosed Newton's method, because easy to implement on 991CW. If you want to see something tricky, try this bisection in spreadsheet, but you can use the definition f(x) on 991CW: 

09242023, 07:32 AM
(This post was last modified: 09242023 07:34 AM by carey.)
Post: #13




RE: Putting Casio fx991CW in perspective.
Csaba,
Thanks for your reply and for these great links! Carey 

09262023, 08:36 AM
Post: #14




RE: Putting Casio fx991CW in perspective.
It has the cross product of two vectors, whereas the 991EX didn't. I also like the fact that all the memory variables can be seen at once. There isn't a calculator which has some minor irritations so on the whole I prefer the 991CW to the 991EX. I use it more than my PRIME and TI CAS.


09262023, 04:54 PM
Post: #15




RE: Putting Casio fx991CW in perspective.
A.) It has the cross product of two vectors, whereas the 991EX didn't.
Simple use product (X) key B.) all the memory variables can be seen at once. thats why RECALL is there C.) some minor irritations IMHO best joke of 2023 Cs. 

09262023, 07:24 PM
Post: #16




RE: Putting Casio fx991CW in perspective.
(09262023 04:54 PM)Csaba Tizedes Wrote: A.) It has the cross product of two vectors, whereas the 991EX didn't. Thanks Csaba: That's what I mean, I had no idea that the cross product can be done on the EX because it isn't in the vector menu, whereas the dot product is. Every calc has its foibles. 

09292023, 09:24 AM
Post: #17




RE: Putting Casio fx991CW in perspective.
A new brainf...  try it on your new gadget, I guess CW same as (C)EX in this field:
A review of builtin equation solver: How to use SOLVE on Elliptic integrals and Separable diffeqs  and many more example. PDF version here: PDF VERSION GOOGLE DRIVE Cs. 

12082023, 07:09 AM
Post: #18




RE: Putting Casio fx991CW in perspective.
See this header pict of a Casio FB page. It shows that the 991CW is the upgrade from the 991ES Plus 2nd Edition. I know, it could've been a Photoshop job. But it does bring up an amusing idea. What do you think?
Casio Calculator.bd 

12082023, 08:46 AM
Post: #19




RE: Putting Casio fx991CW in perspective.
I understand the picture it is time to upgrade from 991es plus 2nd edition to 991cw go for better model:)


12082023, 08:54 AM
Post: #20




RE: Putting Casio fx991CW in perspective.  
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