Section 12: Calculating with Matrices 167

8.Press * to calculate XP = (YX)P. The values of these matrix elements are placed in the result matrix, and the descriptor of the result matrix is placed in the X-register.

9.If you want the product in the form (YX)C, press c

Note that you don't transform XP into .

You can derive the complex elements of the matrix product YX by recalling the elements of (XY)P or (YX)C and combining them according to the conventions described earlier.

Example: Calculate the product ZZ-1, where Z is the complex matrix given in the preceding example.

Since elements representing both matrices are already stored ( in A and (Z-1)Pin B), skip steps 1, 3, 4, and 6.

Keystrokes l>A l>B

Display

 

 

 

A

4

4

Displays descriptor of matrix A.

b

4

2

Displays descriptor of matrix

 

 

 

B.

´<C

*

´U lC

lC lC lC lC lC lC lC ´U

b

4

C

4

C4 C 1,1

1.0000

–2.8500 –10

–4.0000 –11 1.0000 1.0000 –11 3.8000 –10 1.0000 –11

–1.0500 –10

–1.0500 –10

2Designates C as result matrix.

2 Calculates (Z-1)P= (ZZ-1)P.

2Activates User mode.

Matrix C, row 1, column 1. (Displayed momentarily while last key held down.)

Value of c11. Value of c12. Value of c21. Value of c22. Value of c31. Value of c32. Value of c41. Value of c42.

Deactivates User mode.

Page 167
Image 167
HP 15c Scientific manual Keystrokes lA lB Display Displays descriptor of matrix a, ´U lC LC lC lC lC lC lC lC ´U