# Calculators Ti89 error

1. Apr 25, 2004

### Ebolamonk3y

I met such such command for the 89 or the TI series...

ref=gaussian elemination...

rref=refined version of Gaussian...

I wonder who this thing works... Because for the basic circuit problems with like 7 currents... This rref is VERY nifty. If you set up the equations wrong, the answer do not report right and you have to go back and check every darn coefficient again... Then redo the whole thing until it does come out right...

Like, I know that nint uses Newtonian approximation, just want to know how this rref works...

2. Apr 25, 2004

### enigma

Staff Emeritus
It just follows a row reduction algorithm, AFAIK. I programmed a simple one a few years back. The TI-89 most likely has several optimization checks (zeros along the diagonal, etc.) which mine didn't do.
ref is short for "reduce to echelon form"

3. Apr 25, 2004

### Ebolamonk3y

Hmm... so that reduce to echelon form is same as the process of Gaussian elemination?

4. Apr 26, 2004

### enigma

Staff Emeritus
Gauss-Jordan, I believe. Don't know if that's any different from what you're referring to.

I don't know if that's exactly what they do. I know that's one way to do it.

5. Jun 11, 2004

### H-bar None

I know this thread is pretty old but let me put my two cents in.

I have a ti-89. rref ref were my friends in linear algerbra and circuit theory.

rref spat out the solution instantly giving a identity matrix next to the soulutions.

The ref command stopped short, so that x and y coefficients equaled 1. It reduced the amount of operations one would need to complete Gaussian elimination.

I'm talking about a 2x2 matrix with the solution column vector.
It gets real sweet when you have to solve a 3x3 matrix

If my instuctor wanted me to show my work then these commands saved my life during exams.

mRow