First impressions on Casio FX-5800P

[Manolo Sobrino]

Thank you Eddie!

It's strange that this calc isn't more popular. I couldn't find the kind of review I like so I posted one. As you are discovering now it's a remarkable device.

For instance, the solver is pretty capable, it's fast and accurate. You can't specify the interval, though. From reading the manual you could think that it only solves equations of the type X=simple expression, but in fact it will try to solve any equation in the form f(x)=g(x) or F(x)=0. For more variables it treats them as parameters. You can change their values by pressing the EXE key, or solve the equation for any of them by pressing SOLVE again when the editing is done, then the last variable in the problem would be just another parameter. The input value is used as an initial guess and the result is kept as the value for the variable. It shows you the L-R residue and if convergence is slow (for instance x^4=0 with initial guess 2 -kind of a torture test -) it asks you whether you want to continue refining the root value.

I tried the input lag test for the 991ES from Voidware and could type that without problems. Actually it does get sluggish for very long expressions in MathIO, maybe more than 110 characters, that's why I didn't notice it at first. I don't think this has many practical consequences.

It also passes the Voidware integration torture test with better results than those of the 991ES. Accuracy is on par with that of the 4800P and 991ES.

Quibbles after a few weeks of using it sparsely:

1) You can really get weary of menus: typing programs on it or writing two-character formula variables is nothing short of a chore.

2) Shifted STO. When it's faster to do so and I don't need the expressions I just take an approach similar to some ideas in RPN, working inside-out with ANS and the rest of the stack being loosely emulated by registers (yes, there are a few ways to use algebraics). For this, I'd prefer shifted RCL instead... or two primary keys.

Gerald... it's just that IMHO apples and oranges aren't really the best subject for a detailed comparison