Casio FX-991EX and FX-300ES

[Csaba Tizedes]

(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):

integral(1/X, 101325, 200000) * 8.314 / 40644 - integral (1/X^2, 373.15, Z)->Y

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.

Csaba