HP 15c - Manual (Page 138)

138
Section 12
Calculating With Matrices
The HP-15C enables you to perform matrix calculations, giving you the
capability to handle advanced problems with ease. The calculator can work
with up to five matrices, which are named A through E since they are
accessed using the corresponding A through E keys. The HP-15C lets
you specify the size of each matrix, store and recall the values of matrix
elements, and perform matrix operations – for matrices with real or
complex elements. (A summary of matrix functions is listed at the end of
this section.)
A common application of matrix calculations is solving a system of linear
equations. For example, consider the equations
3.8x
1
+ 7.2x
2
= 16.5
1.3x
1
- 0.9x
2
= -22.1
for which you must determine the values of x
1
and x
2
.
These equations can be expressed in matrix form as AX = B, where













2
1
,
0.9 1.3
7.2 3.8
x
x
X A , and 





22.1
16.5
B .
The following keystrokes show how easily you can solve this matrix
problem using your HP-15C. (The matrix operations used in this example
are explained in detail later in this section.)
First, dimension the two known matrices, A and B, and enter the values of
their elements, from left to right along each row from the first row to the
last. Also, designate matrix C as the matrix that you will use to store the
result of your matrix calculation (C = X).