HP HP-15C - Page 171

Section 12: Calculating with Matrices 171
Keystrokes
Display
´> 2
A
4
4
Transforms A
P
into Ã.
´< C
A
4
4
Designates matrix C as
result matrix.
÷
C
4
1
Calculates X
P
and stores
in C.
|c
C
2
2
Transforms X
P
into X
C
.
lC
0.0372
Recalls c
11
.
lC
0.1311
Recalls c
12
.
lC
0.0437
Recalls c
21
.
lC
0.1543
Recalls c
22
.
´U
0.1543
Deactivates User mode.
´> 0
0.1543
Redimensions all matrices
to 0×0.
The currents, represented by the complex matrix X, can be derived from C
















i
i
I
I
2
1
0.15430.0437
0.13110.0372
X
Solving the matrix equation in the preceding example required 24 registers
of matrix memory  16 for the 4×4 matrix A (which was originally entered
as a 4×2 matrix representing a 2×2 complex matrix), and four each for the
matrices B and C (each representing a 2×1 complex matrix). (However, you
would have used four fewer registers if the result matrix were matrix B.)
Note that since X and B are not restricted to be vectors (that is, single-
column matrices), X and B could have required more memory.
The HP-15C contains sufficient memory to solve, using the method
described above, the complex matrix equation AX = B with X and B having
up to six columns if A is 2×2, or up to two columns if A is 3×3.
*
(The
allowable number of columns doubles if the constant matrix B is used as the
result matrix.) If X and B have more columns, or if A is 4×4, you can solve
the equation using the alternate method below. This method differs from the
preceding one in that it involves separate inversion and multiplication
operations and fewer registers.
*
If all available memory space is dimensioned to the common pool (W: 1 64 0-0). Refer to appendix C,
Memory Allocation.