Section 12: Calculating with Matrices 155

For ÷, the matrix specified in the X-register is replaced by its LU decomposition. The ÷ function calculates X–1Yusing a more direct method than does and *, giving the result faster and with improved accuracy.

Example: Using matrices A and B from the previous example, calculate

C = AT B.

⎡1 A = ⎣4

Keystrokes Display l> A A

l> b

B

2

3⎤

1

3

5⎤

 

and B =

 

 

5

9

7

9

17

23 Recalls descriptor for matrix A.

23 Recalls descriptor for matrix B into X-register, moving matrix A descriptor into Y-register.

´<

b

2

3

C

 

 

 

´>5

C

3

3

Designates matrix C as result matrix.

Calculates AT B and stores result in matrix C, which is redimensioned to 3×3.

The result, matrix C, is

⎡29

39

73⎤

 

C = 37

51

95.

90

66

168

Page 155
Image 155
HP 15c Scientific manual = At B, Keystrokes Display l a a