Sunday, November 25, 2012

Matrix Functions on the fx-991ES (fx-115ES in the US) vs TI-36X Pro

Matrix Function Comparison (fx-991ES/fx-115ES vs TI 36X Pro)

Today's blog entry comes from a question by An Artist:

An Artist has left a new comment on your post "TI-36X Pro Review":

Hi Eddie,

In India, the TI 36x pro is available at the same price as the Casio 991ES.
I have ordered the TI.

Is this a good decision?
I've heard of a memory overload bug of the TI which gives wrong answers. Can you please tell me how to get around the bug?

My main focus is matrix and someone told me that this one has more matrix functions for matrices. Can you please confirm that?

Your blogs have been very helpful about calcs. So, keep up the good work.

First of all thank you for the compliment An Artist, very much appreciated.

Regarding the overload bug on the TI-36X Pro, honestly this is the first time I read of it. According to one of the reviewers on the page, the reviewer reports an overload bug occurs when too many equations are used or too much memory is used. I have not found any additional information about this. Personally I have not encounter this problem.

Now the matrix commands. I am going to list the available matrix functions for each calculator. First up, Casio, then Texas Instruments.

Keep in mind both calculators allow only for real-numbered elements.

Casio fx-991ES (aka fx-115ES in the United States)

You will need to enter a specific mode for Matrices (MODE 6)

3 matrices can be stored, up to size 3 x 3 matrices. A separate "Ans" matrix is also available.

Matrix Functions:
Ability to resize matrices
Determinant (dim)
Transpose (Trn)
Inverse (with the x⁻¹ button)
Square of a square matrix (with the x² button)
Cube of a square matrix (with the x³ function)
Absolute Value of each element (Abs)

Matrices are automatically cleared when modes are switched.

Note: The updated fx-115ES PLUS adds the ref and rref functions.

Texas Instruments TI-36X Pro

There is no specific mode required, you can work with matrices directly from the Home screen.

3 matrices can be stored, up to size 3 x 3 matrices. A separate "Ans" matrix is also available. The TI-36X offers identity matrices [I2] and [I3] of size 2 x 2 and 3 x 3, respectively.

Matrix Functions:
Ability to resize matrices (through the edit screen)
Determinant (dim)
Transpose (Trn)
Square of a square matrix (with the x² button)
Powers of a square matrix ([A]^n where n is a positive integer, 0, or -1)
Absolute Value of each element (abs)
Integer Part of each element (iPart)
Fractional Part of each element (fPart))
Rounding of each element (round)
Reduced Echelon Form (ref)
Row Reduced Echelon Form (rref)

Matrices are retained in memory on the TI-36X Pro.

An Artist, to answer your question between the fx-991ES and the TI-36X Pro, I can confirm that the TI-36X Pro has more functions for matrices. Hope this helps,



  1. Thanks man.

    Keep up the good work.

    1. I have received my TI 36X pro and I'm loving it.

      Here is a description of the bug :

      I tried it on mine but I think mine is an updated version with the bug removed.

  2. So is the TI 36X Pro better than Casio FX-991ES Plus? Or only for matrices?

    Internet is full of review but it seems there are not very differences between these 2 nongraphing calculators, isn't it?

  3. yeah man, can u plz tell us which calcs is better casio 991es plus or texas ti 36x pro does both have same no. of functions or ti has more if yes does ti has all the function of casio and which one is more advanced b\w the two

    1. The TI36X Pro is superior to the Casio 115/991ES, because, indeed, matrices are retained in memory on the TI-36X Pro, while they are lost on the Casio, as per Eddie's comments in his review. . . The 36X Pro retains both your calculation history, and your current calculations.

  4. Eddie, I purchased the Casio fx-115es plus and love it. The only issue I have found is in matrix mode. REF is correct, but RREF always shows identity matrix which is incorrect. Some matrices are inconsistent. Thoughts?

  5. Bren,

    RREF works best with matrices of size n x n+1 and I use it primary to solve simultaneous equations. RREF attempts to reduce the matrix of the form:

    [[ 1 0 0 .... ]
    [ 0 1 0 ... ]
    [ 0 0 1 ... ]
    and so on ]

    This is not always the case, RREF reductions lead to something like this:
    [[ 1 0 0 ... ]
    [ 0 0 1 ... ]
    and so on ]

    REF works on getting the matrix to an upper-triangular form, with the goal of getting the diagonals valued at 1.

    I hope this helps,



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