Re: A C H A L L E N G E

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Re: A C H A L L E N G E

Hello,

Rene Kragh Pedersen wrote:
>
> Eric Chu wrote:
> >
> > Hello, TI people.
> >
  [...]

> > Eric Chu
>
> Now come on please, get real. You start of by letting us all know you
> think the HP is superior. It's evident that you aren't going to listen
> to us no matter what.
> However, I want to try and make a few points anyway (how dumb it might
> ever seem :)
>
> You start out by comparing your TI-85 to your HP-48GX and naturally your
> choice has to be the HP. Naturally. But that's like comparing a 486 to a
> P5...Try comparing realistically, for example with TI-92.
> That's when we can start talking, when you compare two equivalent
> calculators, both in functions and time of release into the market.

I don't know when the TI-85 was released exactly, but I want to
point out that the HP48S/SX were released more than four years ago,
when the TI-92 didn't exist yet. Moreover, while the TI-92 is more
oriented towards symbolic manipulations, the HP48 is more oriented
towards numeric calculations, therefore in my opinion the calculators
you want to compare are NOT so equivalent, neither in functions nor
in time of release.


> Example:
> Today I had a math assignment to deliver (I study at the university),
> part of it involved an equation where the solutions were possible limits
> for the expression we were examining. We knew from an earlier part.that
> 3 would be a good guess.
>
> The equation reduced to:
> (a-1)^3 = a+5
>
> I'm lazy, so I don't want to hand-calc (a-1)^3, I just type it on my
> TI-92, pressing: F2 3 (a-3)^3) <ENTER>
> on the screen it said:
> expand((a-1)^3)
> and the result was:
> a^3 - 3a^2 + 3a - 1
> Now, to reduce the right side of my equation to zero, I wanted to move
> (a+5) over, so I pressed <up> <ENTER> - (a+5) <ENTER>
> result:
> a^3 - 3a^2 +2a - 6
> Now, the in the assignment we had to utilize the hunch that 3 was a
> solution, so we needed to divide the expression with (a-3)
> Well, F2 2 <up> <ENTER> , a-3) <ENTER>
> and voila:
> (a-3)(a^2+2)=0
>
> EXACTLY the expression I needed with minimum keypresses.
>
> Try doing it on your HP and see how easy it is to follow and write
> down...One of the other guys here has one and he just said: "well, maybe
> I could write a program that does it *smiling* but no..."
>

I absolutely don't want to start a new flame war between HP and TI
lovers; I owned both of them and enjoyed using both. However, solving
your problem with an HP48 is not so difficult:

- first of all enter the coefficients of ((a-1)^3) as a vector:
   [1 -3 3 -1] (about 12 keystrokes)

- then enter the coefficients of a+5, again as a vector:
   [0 0 1 5] (about 10 keystrokes)

- hit '-' to subtract the two polynomials (1 keystroke); you obtain:
   [1 -2 2 -6] on the stack

- execute the function PROOT (three keystrokes); you obtain:
   [(0, 1.41...) (0, -1.41...) (3,0)]
  This is a vector that represents the three solutions of your
  polynomial: i Sqrt[2], -i Sqrt[2] and 3; two of them are complex
  roots, while the last is a real number. This obviously corresponds
  to the symbolic expression (a^2 + 2)(a - 3) = 0 with the first
  factor factored in the complex domain, too.

Neither the 'hint' you used nor the 'program' you mentioned are
needed in any way.

I just want to say that, in order to compare two different tools in
any way, as a minimum you must be able to use well BOTH of them.

I agree with you that the TI-92 is easier to use; however, I think
this isn't the right example to support this opinion.

With my best wishes,

--
------------------------------------------------------------------------
Ivan Cibrario Bertolotti                | Phone: +39-11-3919246
Television Study Center of the National | Fax:   +39-11-341882
Research Council, Turin (Italy)         | Email: cibrario@cstv.to.cnr.it
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