Re: using the Root function with Algebraic and RPL

On Jul 17, 7:10 pm, "John H Meyers" <jhmey...@xxxxxxxxxxxxxx> wrote:
Previously:

We can reproduce it [apparent bug on HP49/50 series]

\<< X X * 1 - \>> 'A' STO

In "Y=" window, press ADD and enter 'Y1(X)=A'

Press ERASE and DRAW; the graph is correctly drawn.

If we press TRACE, the graph can be correctly traced.

FCN followed by ROOT or ISECT, however,
may result in no solution ("Constant?")

[whereas it's fine on original HP48[S/G] series]

Here's how to pacify the HP49/50 series' CAS:

\<< \-> X \<< X X * 1 - \>> \>> 'A' STO

In "Y=" window, press ADD and enter 'Y1(X)=A(X)'

Now you can both graph _and_ numerically solve (ROOT, ISECT).

Why did the CAS *** in to mess with the _numeric_ root finder,
particularly when there was even nothing algebraic whatsoever involved?

I.E. even 'A' 'X' 0 ROOT worked on HP48S/G
but failed on HP49/50 in the original case;
after above modification of 'A' we must instead try

'A(X)' 'X' 0 ROOT (now pacified, even on HP49/50)

[r->] [OFF]

John-

Thanks very much for the detailed discussion, testing results, and
solution.

I was able to modify my variables per your solution and make the
addition using Y=.

Works every time. Also tried a couple other examples as well which
also work.

More importantly, I have learned a lot.

Randy

.