Finally I decided to purchase a Casio FX-991EX even though I already got the FX-300ES
I have been using this 300ES a lot when study math stuff this calculator price is very cheap compare to it features and functions.
Until yesterday I buy another one but now the 991EX because of many positive reviews. This one is a little more expensive than 300ES when I got it but the features and functions is much more and computation speed is very fast.

The photos attached gave the comparison look and noticed the inside slide cover of the 300ES came with the basic instructions.

I have only one question - and if is it true, I'll buy a 991EX: The SOLVE can handle integrate and / or differentiate? For example, I want to know the integral interval width or I want to solve a differential equation, this means I must to solve for upper or lover limit of interval.

SOLVE can handle these two functions together? For example I want to solve mechanics problems like work-theorems (Betti's theorem).

(12-24-2017 05:50 PM)Csaba Tizedes Wrote: [ -> ]I have only one question - and if is it true, I'll buy a 991EX: The SOLVE can handle integrate and / or differentiate? For example, I want to know the integral interval width or I want to solve a differential equation, this means I must to solve for upper or lover limit of interval.

SOLVE can handle these two functions together? For example I want to solve mechanics problems like work-theorems (Betti's theorem).

Thanks,
Csaba

The 991 DE X can solve for upper or lower limit of an integral. eg for the upper limit of integral of 1/ln(x) with a lower limit of 2 & some value for the integral.

The fx-991CE X is better option then fx-991ex, more functions and is in "magyar" (the other languages are czech, slovak and polish - CE means central europe). https://www.alza.hu/casio-fx-991-ce-x-d5088312.htm

This version differs a little bit compared to the fx-991de x.
CE version has periodic table, but there is no functions like product, GCD, LCM, Int, Intg, RndFix
I recommend to you try your calculations in the emulator. http://edu.casio.com/softwarelicense/index.php

I have all three calcs and all three calcs accept d/dx and integrals in the solve capabilities. Another question is how difficult is the integral or d/dx and how much the computations consume time

Following examples by using fx-991EX
solve d/dx(x^3+5x^2-2x-5)=0/x=A
A=0.189, A=-3.523

solve integral(x/sqrt(1+x^2),0,A)=19
A=19.975 after 33s,

I have tried how can I solve with it simple ODE, and it works. Check the attachment. (Solving Clausius-Clapeyron ODE - the problem: what is the boiling temperature of water if the pressure is 2 bara). I can do it with my another CASIO with numeric integration but requires some iteration to find the solution (T_boiling= 393.6K= 120.4°C)

The greatest fault: Unfortunately the English is not selectable if I'll buy CE version.

Hello,
I tried it with Casio fx 5800p, which has Solver but prohibiting integral or d/dx within it: combined with a very small secant method program, I introduced this formula in a separate subroutine (under the form f(Z)->Y, to solve for Z):

(12-26-2017 09:58 AM)Pekis Wrote: [ -> ]Hello,
I tried it with Casio fx 5800p, which has Solver but prohibiting integral or d/dx within it: combined with a very small secant method program, I introduced this formula in a separate subroutine (under the form f(Z)->Y, to solve for Z):

Result: 393.57804, after 18 iterations starting from Z=2, in approx. 35 sec.

Yes, this is the method to solve ODE if you do not need the general solution, only want to know the result in a given point. The Classwiz can to handle it without programming, but it was little confusing when I tried similar way as you wrote:

SOLVE(...-integral(1/X^2,373.15,A),A) - gives No Root Found
SOLVE(...-integral(1/X^2,373.15,X)) - gives X=393.5....

As I try to use the emulator it seems to me the fx-50FII is better option, because it is programmable. I will check the user manual of 50FII, if no subroutine possibility, that is really bad news - again.

Why the CASIO can't produce a very professional calculator like 4000P was in the 80's?!? With integration, differentiation, subroutines, lots of memory, USB.

(12-26-2017 12:06 PM)Csaba Tizedes Wrote: [ -> ]... As I try to use the emulator it seems to me the fx-50FII is better option, because it is programmable. I will check the user manual of 50FII, if no subroutine possibility, that is really bad news - again.

Why the CASIO can't produce a very professional calculator like 4000P was in the 80's?!? With integration, differentiation, subroutines, lots of memory, USB.

Csaba

Hello,
It seems the Casio fx-5800p is not bad at all, with a rather good function set and satisfying programming possibilities, which make me forgive it's limitations ... The Casio 991 Classwiz are good but you're stuck with no programming, and other lower-priced Casio are too limited ...

I use Unicode 22bf to get the right triangle character. (⊿) I have to post that Unicode character from a comparable software like WordPad, NotePad, or Word.

Where:
X1 and X2 are the initial values
T is the target value for y=f(x), ie solve f(x)-T=0
The function f is contained in Prog"YFX", calculating Y=f(X) the way you like
The program displays each intermediate X value and you have to press EXE to continue until OK for you

(12-26-2017 12:06 PM)Csaba Tizedes Wrote: [ -> ]method to solve ODE if you do not need the general solution (...) Classwiz can to handle it without programming:

The constant in the equation is C= 2258_kJ/kg × 0.018_kg/mol ÷ 8.314_J/(mol×K) = 4889_K