HP 15c User Manual

Page 139

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Section 12: Calculating with Matrices 139

Keystrokes

Display

| " 8

Deactivates Complex
mode.

2

v ´ m A

2.0000

Dimensions matrix A
to be 2×2.

´ > 1

2.0000

Prepares for automatic
entry of matrix
elements in User mode.

´ U

2.0000

(Turns on the USER
annunciator.)

3.8

O A

A 1,1 Denotes matrix A, row

1, column 1. (A display
like this appears
momentarily as you
enter each element and
remains as long as you
hold the letter key.)

3.8000

Stores a

11

.

7.2

O A

7.2000

Stores a

12

.

1.3

O A

1.3000

Stores a

21

.

.9

“ O A

-0.9000

Stores a

22

.

2

v 1 ´ m

B

1.0000

Dimensions matrix B to
be 2×l.

16.5

O B

16.5000

Stores b

11

.

22.1

“ O B

-22.1000

Stores b

21

.

´ < C

-22.1000

Designates matrix C
for storing the result.

Using matrix notation, the solution of the matrix equation AX = B is

X = A

-1

B

where A

–1

is the inverse of matrix A. You can perform this operation by

entering the ―descriptors‖ for matrices B and A into the Y- and X-registers
and then pressing ÷. (A descriptor shows the name and dimensions of a
matrix.) Note that if A and B were numbers, you could calculate the answer
in a similar manner.

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