Section 12: calculating with matrices, Calculating with matrices – HP 15c User Manual

Page 138

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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).

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