I know this is a long time ago, but i am sure someone might ask eventually this same question.For the Casio fx-115es here are the instructions:go to mode, matrix, and pick the matrix you want to you.. you only have 3 options.create your matrix and press AC.Here is the tricky part, DO NOT go to mode again, that will reset your matrices that you have entered. Instead, press shift and the number 4 key, which is also matrix, go to press 1 (DIM), chose the other matrix to enter, and you can start mult, adding, etc.Any time you want to use the entered matrices, go through the matrix function, not the mode function.
Hello,
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.
Hope it helps.
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