There has been a lot of messages concerning trig. functions for the HP-12C.

Here is a new math theme for the HP-12C fans:

**3x3 MATRIX OPERATIONS FOR THE HP-12C**

I wrote this program some times ago. I just wanted to see if it is possible to program any 3x3 matrix operations for the HP-12C.

And it was possible...

This program uses Cramer's rule to solve systems of linear equations with 3 unknowns.

In matrix form AX=B.

PROGRAM LISTING

01 0

02 STO 0

03 RCL 5

04 RCL 9

05 *

06 RCL 6

07 RCL 8

08 *

09 -

10 RCL 1

11 *

12 RCL 4

13 RCL 9

14 *

15 RCL 6

16 RCL 7

17 *

18 -

19 RCL 2

20 *

21 -

22 RCL 4

23 RCL 8

24 *

25 RCL 5

26 RCL 7

27 *

28 -

29 RCL 3

30 *

31 +

32 RCL 0

33 X=0?

34 GTO 41

35 /

36 R/S

37 1

38 CHS

39 STO*0

40 GTO 44

41 RDN

42 STO 0

43 /

44 RCL 1

45 RCL 2

46 RCL 3

47 RCL n

48 STO 3

49 RDN

50 STO 2

51 RDN

52 STO 1

53 RDN

54 STO n

55 RCL 4

56 RCL 5

57 RCL 6

58 RCL i

59 STO 6

60 RDN

61 STO 5

62 RDN

63 STO 4

64 RDN

65 STO i

66 RCL 7

67 RCL 8

68 RCL 9

69 RCL PV

70 STO 9

71 RDN

72 STO 8

73 RDN

74 STO 7

75 RDN

76 STO PV

77 GTO 03

USER INSTRUCTIONS

1) Key in the program

2) Store elements of matrix A into registers R

_{1}through R

_{9}

3) Store elements of matrix B into registers n, i and PV

4) Press [f] [PRGM] [R/S] to calculate x

_{1}

5) Press [R/S] to calculate x

_{2}

6) Press [R/S] to calculate x

_{3}

7) Press [R/S] once again to return elements of matrices A and B into their original registers (-1.00 will be displayed)

8) For a new case, go to step 2 or 3.

Rem: If Det A=0, then the system is linearly dependent and this program is not applicable (Error 0 will be displayed)

Ref: For example HP-34C Mathematics Applications Book