HP 39gs Master Manual page 197

INVERSE(<matrix>)
This function produces the inverse matrix of an n x n square matrix,
where possible. A fully worked example of the use of an inverse matrix
to solve a 3 by 3 system of equations is given in the chapter on Using
Matrices on page 211 and in Appendix A on page 302.
An error message is given (see right) when the matrix is singular (det.
zero).
Note:
Some people write the inverse matrix as a fraction (one over the
determinant) multiplied by a matrix, so as to avoid decimals and
fractions within the inverse matrix. The calculator does not do
this. If you want the matrix with the determinant factored out,
then evaluate
DET(matrix)
evaluate
DET(matrix) * INVERSE(matrix)
a non-fractional matrix.
⎡ 2 3 ⎤
A = ⎢ ⎥ ⇒ A
i.e.
⎣ 4 5 ⎦
Remember that the inverse matrix is not just the matrix, but the fraction
times the matrix.
See also: ,
RREF DET
LQ(<matrix>)
This function takes an mxn matrix, factors it and returns a list containing three matrices which are (in order):
an mxn lower trapezoidal matrix
•
an nxn orthogonal matrix
•
• an mxm permutation matrix.
If you want to separate these matrices for later use then you should store them into a list variable.
For example, if was [[1,2,3],[4,5,6],[7,8,9]] then
M1
into list variable . In the
L1
into and so on.
M2
first, record the fraction and then
− 3
1 ⎡ 5 ⎤
−
=
1
− 2 ⎣ ⎢ − 4 ⎥
2 ⎦
view you could now enter
HOME
to obtain (usually)
would store the three resulting matrices
LQ(M1) L1
to store the first of the result matrices
L1(1) M2
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