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

3.8x1 + 7.2x2 = 16.5 1.3x1 - 0.9x2 = -22.1

for which you must determine the values of x1 and x2.

These equations can be expressed in matrix form as AX = B, where

3.8

7.2

,

x1

, and

16.5⎤

A =

X =

B =

.

1.3

− 0.9

 

x2

 

− 22.1

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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HP 15c Scientific manual Calculating With Matrices, 138