Keystrokes display – HP 15c User Manual
Page 129
Section 4: Using Matrix Operations
129
Keystrokes
Display
´>5
073-42,16, 5
Calculates C = B
T
A.
l>B
074-45,16,12
´<A
075-42,26,11
*
076- 20
Calculates A = B
T
AB.
tA
077- 22 11
Labels used: A, 0, 1, 2, and 3.
Registers used: R
0
, R
1
, R
2
(off-diagonal sum), and R
3
(||A
j
||
F
).
Matrices used: A (A
j
), B (Q
j
), and C.
To use the program:
1. Press 4 ´m% to reserve registers R
0
through R
4
.
2. Press ´U to activate User mode.
3. Dimension and enter the elements of matrix A using ´mA
and OA.
The dimensions can be up to 4 × 4, provided that there is sufficient memory available
for matrices B and C having the same dimensions also.
4. Press A to calculate and display the off-diagonal ratio.
5. Press ¦ repeatedly until the displayed ratio is negligible, say less than 10
−8
.
6. Press lA repeatedly to observe the elements of matrix A. The diagonal
elements are the eigenvalues.
Example: What quadratic surface is described by the equation below?
3
2
1
3
2
1
4
3
2
3
2
1
2
1
0
x
x
x
x
x
x
T
Ax
x
= 2
2
1
x
x
+ 4
3
1
x
x
+ 2
2
2
x
+ 6
3
2
x
x
+ 4
3
3
x
= 7
Keystrokes
Display
|¥
Run mode.
4
´m%
4.0000
Allocates memory.
´U
4.0000
Activates User mode.
3
v´mA
3.0000
Dimensions A to 3 × 3.
´>1
3.0000
Sets R
0
and R
1
to 1.
0
OA
0.0000
Enters a
11
.
1
OA
1.0000
Enters a
12
.