My calculator fx-991 Es is showing either syntax error or dimension error while finding out the inverse of the matrix although the matrix is a square one

The Casio FX-570MS does not handle matrices. So you cannot create matrices, let alone invert them. Sorry.
The Casio FX115 ES handles matrices for up to 3X3 dimension. Create the matrix.Have its name displayed on the command line and press the [x^-1] (reciprocal ) key.

The following was written for the Casio FX-991 ES. If matrix calculations are available on your calculator you will perform them as described below. ( I have no time to verify that the FX-991ms can perform matrix calculations).

Let me explain how to create matrices. (If you know how to do it, skip to the operations on matricies, at the end.)

First you must set Matrix calculation
[MODE][6:Matrix]. Then By entering one of the numbers [1:MatA] or [2:Matb] or [3:MatC] you get to choose the dimensions of the matrix
(mxn]. Once finished entering the matrix you clear the screen.
The operations on matrices are available by pressing [Shift][Matrix]
[1:Dim] to change the dimension of a matrix (in fact redefining the matrix)
[2:Data] enter values in a matrix
[3:MatA] access Matrix A
[4:Matb] access Matrix B
[5:MatC] access matrix C
[6:MatAns] access the Answer Matrix (the last matrix calculated)
[7:det] Calculate the determinant of a matrix already defined
[8:Trn] The transpose of a matrix already defined

To add matrices MatA+MatB
To subtract MatA-MatB
To multiply MatAxMatB
To raise a matrixe to a power 2 [x2], cube [x3]
To obtain inverse of MatA already defined MatA[x-1] [x-1] is the x to the power -1 key
Dimensions of matrices involved in operations must match.
Here is a short summary

The multiplication of structured mathematical entities (vectors, complex numbers, matrices, etc.) is different from the multiplication of unstructured (scalar) mathematical entities (regular umbers). As you well know matrix multiplication is not commutative> This has to do with the dimensions.

An mXn matrix has m rows and n columns. To perform multiplication of an kXl matrice by an mXn matrix you multiply each element in one row of the first matrix by a specific element in a column of the second matrix. This imposes a condition, namely that the number of columns of the first matrix be equal to the number of rows of the second.
Thus, to be able to multiply a kXl matrix by am mXn matrix, the number of columns of the first (l) must be equal to the number of rows of the second (m).

So MatA(kXl) * MatB(mXn) is possible only if l=m
MatA(kX3) * Mat(3Xn) is possible and meaningful, but
Mat(kX3) * Mat(nX3) may not be possible.

To get back to your calculation, make sure that the number of columns of the first matrix is equal to the number of rows of the second. If this condition is not satisfied, the calculator returns a dimension error. The order of the matrices in the multiplication is, shall we say, vital.

Not all matrices are invertible. The matrice must be square.The matrix must be non-singular: Its determinant must be different from 0. Your error comes probably from the key you used to calculate the inverse. Use the reciprocal key, the one marked with x^-1. If the marking is not ON the key, use the SHIFT button prior to pressing the relevant key.

Press SHIFT [MATRIX], specify the matrix to be inverted, then x^-1.

Example #103 in the appendix shows the exact procedure for inverting the matrix entered in example #096. If you need the manual and the appendix, you can download them from
http://support.casio.com/manualfile.php?rgn=1&cid=004001004

The FX-991ES offers simple matrix operations like basic arithmetic, plus the slightly more complex operations determinant and inversion. Furthermore, it is limited to matrices with a maximum size of three rows and three columns.

The rank of a matrix is defined as the number of linearly independent row or column vectors. You can perform a simple partial test for square matrices by calculating the determinant of the matrix:

1. Enter the matrix into matrix variable MatA.
2. Press [SHIFT] [4] [7] [SHIFT] [4] [3] [)] [=]

The display now should show det(MatA) and the determinant of the matrix in the result. If the determinant is not 0, the rank of the matrix equals the dimension of the matrix, otherwise the rank is less than the dimension.

Unfortunately, this is all support the calculator offers. For small matrices (i.e. 4x4 or smaller), you should familiarize yourself with the Gau? Elimination Method algorithm for solving linear equation systems. It is a two-step procedure where a matrix first is converted to its row echelon form, and second to row canonical form to solve the LES.
You need to follow the algorithm only through the first part, the number of non-zero rows after this step equals the rank of the matrix. With a little exercise you will be able to do it faster on paper than trying to do it with your calculator only.

For larger matrices I suggest to use a PC with more powerful math software (Maple, Mathematica, ...) or, if you know some basic computer programming, just write the necessary program yourself, which is also a very good exercise both in programming and understanding the algorithm.

This post is rather exhaustive as regards the matrix capabilities of the calculator. So if the post recalls things you already know, please skip them. Matrix multiplication is at the end.

Let me explain how to create matrices. (If you know how to do it, skip to the operations on matrices, at the end.)

First you must set Matrix calculation
[MODE][6:Matrix]. Then By entering one of the numbers [1:MatA] or [2:Matb] or [3:MatC] you get to choose the dimensions of the matrix
(mxn]. Once finished entering the matrix you clear the screen.
The operations on matrices are available by pressing [Shift][Matrix]
[1:Dim] to change the dimension of a matrix (in fact redefining the matrix)
[2:Data] enter values in a matrix
[3:MatA] access Matrix A
[4:Matb] access Matrix B
[5:MatC] access matrix C
[6:MatAns] access the Answer Matrix (the last matrix calculated)
[7:det] Calculate the determinant of a matrix already defined
[8:Trn] The transpose of a matrix already defined

To add matrices MatA+MatB (MUST have identical dimensions same m and same n, m and n do not have to be the same)
To subtract MatA-MatB. (MUST have identical dimensions, see above)
To multiply MatAxMatB (See below for conditions on dimensions)
To raise a matrix to a power 2 [x2], cube [x3]
To obtain inverse of a SQUARE MatA already defined MatA[x-1]. The key [x-1] is the x to the power -1 key. If the determinant of a matrix is zero, the matrix is singular and its inverse does not exit.

Dimensions of matrices involved in operations must match. Here is a short summary

The multiplication of structured mathematical entities (vectors, complex numbers, matrices, etc.) is different from the multiplication of unstructured (scalar) mathematical entities (regular numbers). As you well know matrix multiplication is not commutative> This has to do with the dimensions.

An mXn matrix has m rows and n columns. To perform multiplication of an kXl matrix by an mXn matrix you multiply each element in one row of the first matrix by a specific element in a column of the second matrix. This imposes a condition, namely that the number of columns of the first matrix be equal to the number of rows of the second.
Thus, to be able to multiply a kXl matrix by am mXn matrix, the number of columns of the first (l) must be equal to the number of rows of the second (m).

So MatA(kXl) * MatB(mXn) is possible only if l=m
MatA(kX3) * Mat(3Xn) is possible and meaningful, but
Mat(kX3) * Mat(nX3) may not be possible.

To get back to your calculation, make sure that the number of columns of the first matrix is equal to the number of rows of the second. If this condition is not satisfied, the calculator returns a dimension error. The order of the matrices in the multiplication is, shall we say, vital.

The enclosed screen capture shows all the possible dimensions for matrices on the Casio FX-991ES. As you can see the maximum dimension of any matrix is 3. You can only create matrices with dimensions less than or equal to 3.

The same way you would get the inverse of a number. Assuming you already have the matrix entered into memory, press SHIFT 4 to bring up the matrix menu, select the matrix whose inverse you want, then press the x^-1 key (just to the right and slightly below the big round cursor pad.

Hello,

The error may be due to the key you used to signifie inverse. It says in the manual that you should use the key x^-1 not the one used to input general powers.
Here is screen capture from the Appendix to the manual. The picture shows the sequence of keys to press to obtain the inverse of a 2x2 matrix. It is taken from page 41 of Appendix


The matrix used in the exemple is
a_11=2 a_12=1 a_21=1 a_22=2
Here is the link to download the manual and the appendix

http://support.casio.com/manualfile.php?rgn=1&cid=004001004

Hope it helps

Hello,
You cannot calculate the inverse of an arbitrary matrix. It must be a square matrix (nxn) with non zero determinant. Make sure dimensions m and n are equal. (2x2), (3x3)

To calculate its determinant [Shift][MATRIX] [7:det] [SHIFT][MATRIX][3:MatA] close the right parenthesis and [=].
If determinant is different from zero then you can calculate its inverse.
If matrix MatA has already been defined, you calculate its inverse as follows;
[SHIFT][MATRIX][3:MatA] [X^-1][=]. Use the X to -1 power , the one under [MODE].
For well-behaved matrices you calculate the inverse directly without worrying about the determinant.
Hope it helps.