Retro Review: TI-68

[jhallen]

My latest acquisition is a fully working TI-68. I already had a TI-68, but with the usual ribbon cable / LCD problems (someone needs to find a fix for this).

Anyway, this is a great complex number formula (non-programmable) calculator. Nearly all functions accept complex arguments. The one disappointment is that factorial is whole number only.

So e^(0, pi) gives (-1, -2.2*10^-13), almost :-)

Its SIMUL function can solve systems of linear equations with complex coefficients, really nice for impedance calculations.

Its POLY function finds all complex roots of up to fourth order polynomials.

It has numeric integration, but it does not seem to have a numeric root finder. It has a "SOLVE" button, but this should be called evaluate- you use it to evaluate formulas.

I think the user interface is kind of weird. There is a key to choose the output mode, rectangular or polar. But it does not convert the current number. There is another key for that, P->R. In polar mode, it reduces any number you enter to -180 to 180 or -pi to pi.

There is a separate key for 2's complement (for binary/hex/octal modes), but as far as I can tell it is completely identical to negate (-), so redundant.

It has real and imag keys- they extract the first or second part of the complex number argument. So if the argument has a complex number in polar form, imag returns the angle.

It has the percent change key- I thought only HP calculators had this.