(12C) Determinant of the 3x3 Matrix

[Albert Chan]

(12-08-2018 01:59 PM)Dieter Wrote:  Take a look at the keyboard. The numbers 1 through 9 are nicely arranged like the elements of a 3x3 matrix.
Simply store the respective element in the register with the same position on the keyboard!

It would work even better if the keyboard shape like a telephone.
That way, the Cj input method match direct memory-store method. (No sign change needed)

I would suggest forget about the shape of keyboard, and store the numbers to R1, R2, R3 ...
So, both input methods get the same answer.

It also helps when lookup the registers: R1 = first number (instead of R7)

Edit: program can be shortened to 30 steps (possibly slightly faster too)
Assuming above suggested input method:

Code:

RCL 5 RCL 9 × RCL 6 RCL 8 × − RCL 1 ×
RCL 4 RCL 9 × RCL 6 RCL 7 × − RCL 2 × −
RCL 4 RCL 8 × RCL 5 RCL 7 × − RCL 3 × +
GTO 00