TI-89 Calculator and Systems Of Linear Equations

Well, I finally went out and bit the bullet. I purchased the TI-89 Titanium. I have to say that for the price I paid, I'm not wildly impressed. The display is not at all vivid or strong, and the keyboard is anything but intuitive.

However, I'm posting/griping about a particular issue. The calculator comes with a particular program, a Simultaeneous equation solver, which is precisely what I purchased it for. It's actually a pretty good program, in terms of data entry, but it has one major idiosyncracy (at least that I've found so far): When I put in equations with complex coefficients, as often as not it reports results with complex values in the denominators, along the lines of:

..345/(1.34 + 2.3j)

Sometimes the solution is even more complicated, in the form of

(a + bi)/(c+di)

It seems a no brainer to me that the calculator should automatically do the work of clearing the complex value from the denominator, giving me a nice, simple

Does anyone know if there is a simple, one-button way to tell the program to flush the complex numbers from the denominator, to give me the simple result that I need?

Thanks in advance for all replies.

Steve O.

that is very strange.

okay, one thing though, i was talking about TI 89 (not TI 89 Titanium, although I heard both have the same capabilities, but the Titanium has more flash ram or whatever)

in any case, i strongly believe it works.

tell me one thing... what happens when you press the diamond and press enter, does it simplify then ? (in my TI 89, the diamond is a agreen button, and when you press that and press "enter", that is same as ~= ...i.e. approximate) try that and tell me what happens then

(but unfortunately though, when you do that, you'll lose the fractions and get the exact values.. so for example 1/2 + 3/4i actually becomes

anyway, see what happens when you do that.

SCO wrote:

SCO, you are using a variable 'i' rather than the i of imaginary. You get the imaginary i by pressing 2nd followed by the 'catalog' button.

-- john

AAAH... that could be it dude. use the yellow "i" (it looks FATTER than an ordinary "i")

John O'Flaherty wrote:

Where you clearly typed in something incorrectly, or in the wrong order, or through misunderstanding.

....when working to three decimal accuracy, and a sledgehammer to kill a fly.

On the other hand, having had the practice, it takes only a few

(2 + i)/(2 - 3i) = [(2 + i)/(2 - 3i)]/[(2+3i)/(2+3i)] =[4 - 3 + 8i] / [4 + 9] =(1 + 8i)/13

....not so easy to type or see in ASCII, as it is to write it quickly on the page.

This is done in high schools here, where students [OK, most] do generate the skill prior to college entry, and learn useful terms such as "difference of squares" and "complex conjugate" at the same time.

Doh!!

Thank you. I'll try this at home later.

Original poster, posting from an alternate e-mail address.

Steve O.

John O'Flaherty wrote:

Thanks for the suggestion, but no, not me for it's not. At least, not when I am in that program (Simulateous Equation Solver). I press up arrow to highlight the solution, and then press , but the solution in the form of (a + bi)/(c + di) just "sits" there, without reducing to g+ ei.

Worse yet, even in basic "command line" mode, typing an expression like (2+i)/(2-3i) gives me

-.3333 * (i + 2) / (i - .666666)

when I should be seeing 0.077+0.615 i

(results courtest of Mathcad).

I've also tried changing the Mode of the complex format from Real to Rectangular to Polar, and as far as I can tell, that does nothing!! Is there a bug in the software (gee, that would be a surprise....), or am I missing a trick here.

Steve O.