HP 15c Scientific in C, to 0×0, Recalls c11, Recalls c12, Recalls c21, Recalls c22, result matrix, Transforms AP into Ã, Transforms XP into XC, Deactivates User mode

	Section 12: Calculating with Matrices 171
Keystrokes	Display
´>2	A	4	4	Transforms AP into Ã.
´<C	A	4	4	Designates matrix C as
				result matrix.
				Calculates XP and stores
÷	C	4	1	in C.
c	C	2	2	Transforms XP into XC.
lC	0.0372			Recalls c11.
lC	0.1311			Recalls c12.
lC	0.0437			Recalls c21.
lC	0.1543			Recalls c22.
´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

X= ⎡I1 ⎤ = ⎡0.0372+ 0.1311i⎤ ⎢⎣I2 ⎥⎦ ⎢⎣0.0437+ 0.1543i⎥⎦

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.