(35S) Determinant of a 3x3 matrix (plus cross product): the shortest way.

06262022, 07:42 AM
(This post was last modified: 06282022 07:02 PM by Roberto Volpi.)
Post: #1




(35S) Determinant of a 3x3 matrix (plus cross product): the shortest way.
Taking advantage of the HP35S vector support, a determinant of a 3x3 squared matrix can be computed with just 10 lines of programs:
001 LBL M 002 XEQ X 003 STO G 004 SF 10 005 (EQN) 3RD VECTOR 006 CF 10 007 (EQN) [REGZ, REGY, REGX]* 008 RCL G 009 x 010 RTN * to insert REGX in program mode press EQN, R down, and select X INSTRUCTIONS: The elements of our 3x3 matrix will be input as row vectors, just by typing the values separated by ENTER. EX. calculate the determinant of the following 3x3 matrix: [3, 5, 2 9, 7, 2 11, 0, 0]  input the 1st row: 3 ENTER 5 ENTER 2  press XEQ M and the HP35S will display: 2ND VECTOR  input the 2nd row: 9 ENTER 7 ENTER 2  press R/S and the HP35S will display: 3RD VECTOR  input the 3rd row: 11 ENTER 0 ENTER ENTER (as the "0" is repeated)  press R/S and the HP35S will display the result: 44 It does not work? Well, also the subroutine X needs to be inserted. It is a short standalone program of just 10 lines to compute the cross product of a 2 vectors of 3 elements. 001 LBL X 002 SF 10 003 STO C 004 R down 005 STO B 006 R down 007 (EQN) 2ND VECTOR 008 CF 10 009 (EQN) [BxREGXCxREGY,CxREGZREGTxREGX,REGTxREGYBxREGZ] 010 RTN INTRUCTIONS: The elements of our vectors will be input just by typing the values separated by ENTER. EX. calculate the cross products of these 2 vectors: [3, 5, 2] and [9, 7, 2]  input the 1st vector: 3 ENTER 5 ENTER 2  press XEQ X and the HP35S will prompt: 2ND VECTOR  input the 2nd vector: 9 ENTER 7 ENTER 2  press R/S and the HP35S will display the result: [4, 12, 24] Enjoy! Put a calculator into your life! 

06262022, 08:52 AM
Post: #2




RE: (35S) Determinant of a 3x3 matrix (plus cross product): the shortest way.
Somewhat related from HP 35s  my first thoughts: Message #20:
Code: X001 LBL X Now that we have the crossproduct of two vectors it's easy to calculate the determinant: just calculate the scalar product with the third vector. 

06262022, 09:01 AM
Post: #3




RE: (35S) Determinant of a 3x3 matrix (plus cross product): the shortest way.
You might also be interested in these links:


06262022, 09:07 AM
(This post was last modified: 06262022 09:09 AM by Roberto Volpi.)
Post: #4




RE: (35S) Determinant of a 3x3 matrix (plus cross product): the shortest way.
(06262022 09:01 AM)Thomas Klemm Wrote: You might also be interested in these links: The list of related items may be in fact endless. Matrices are an interesting subject and lot of HP35S users have submitted great programs to add matrix calculation features, à la HP15C. Put a calculator into your life! 

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