Imaginary Matrix Division

08212021, 02:57 AM
Post: #1




Imaginary Matrix Division
The Prime does this:
[[1 1][1 1]] / [[1 1][1 i]] [[1 1][0 0]] Most other calculators get [[1 0][1 0]] for an answer. Which is right? Tom L Cui bono? 

08212021, 06:17 AM
Post: #2




RE: Imaginary Matrix Division
(08212021 02:57 AM)toml_12953 Wrote: The Prime does this: The 50g also gets [[1 1][0 0]]. Wolfram Alpha returns [[1 1][1 i]]. Hmmm. <0ɸ0> Joe 

08212021, 06:43 AM
Post: #3




RE: Imaginary Matrix Division
Interesting, matrix multiplication is not commutative.
If a = [[1 1][1 1]] and b = [[1 1][1 i]] When ask Prime a/b gives a warning: inv(b)*a This gives [[1 1][0 0]] If you do a*inv(b) gives [[1 0][1 0]] For me exponents should be operate first so prime in this misleading expresión is correct. But I am not sure, could be the opposite. Toni 

08212021, 08:05 AM
Post: #4




RE: Imaginary Matrix Division
(08212021 06:17 AM)Joe Horn Wrote:(08212021 02:57 AM)toml_12953 Wrote: The Prime does this:The 50g also gets [[1 1][0 0]]. Same result, as early as the 28S, and even the HP71B w/ Math ROM (doing INV(B)*A ). (08212021 06:43 AM)Tonig00 Wrote: When ask Prime a/b gives a warning: inv(b)*a RPL machines (since the 28S) were implementing the "matrix division" a/b as inv(b)*a. JF 

08212021, 09:29 AM
(This post was last modified: 08212021 09:30 AM by Werner.)
Post: #5




RE: Imaginary Matrix Division
(08212021 06:17 AM)Joe Horn Wrote: Wolfram Alpha returns [[1 1][1 i]]. Hmmm. That is the result of an elementwise division.. Matrix division being implemented as premultiplying by the inverse was already present in the 42S. Since [[1 1][1 1] has 2 identical colums, so will the result. Cheers, Werner 41CV†,42S,48GX,49G,DM42,DM41X,17BII,15CE 

08212021, 11:21 AM
(This post was last modified: 08212021 11:26 AM by Albert Chan.)
Post: #6




RE: Imaginary Matrix Division
(08212021 09:29 AM)Werner Wrote: Matrix division being implemented as premultiplying by the inverse was already present in the 42S. Matrix "division" B/A is really solving for A*X = B for X, without gettting inv(A) It is faster and likely more accurate. https://www.hpmuseum.org/forum/thread14...#pid128492 https://www.hpmuseum.org/cgisys/cgiwrap...read=65551 

08212021, 01:29 PM
Post: #7




RE: Imaginary Matrix Division
(08212021 11:21 AM)Albert Chan Wrote: Matrix "division" B/A is really solving for A*X = B for X, without gettting inv(A) Of course ;) usually I’m the one telling others. I’m slipping.. Xheers, Werner 41CV†,42S,48GX,49G,DM42,DM41X,17BII,15CE 

08222021, 05:22 PM
Post: #8




RE: Imaginary Matrix Division
Is there a reason to not support both left and right division of matrices?


08232021, 11:57 AM
Post: #9




RE: Imaginary Matrix Division
You would need a new symbol, perhaps B/A for left and B\A for right; but that may be more confusing than not supporting both.


08232021, 05:30 PM
Post: #10




RE: Imaginary Matrix Division
(08232021 11:57 AM)roadrunner Wrote: You would need a new symbol, perhaps B/A for left and B\A for right; but that may be more confusing than not supporting both. In algebraic mode, there certainly could be a bit of confusion as to which is the dividend and which is the divisor in B\A (this wasn’t a problem in math classes I attended where left and right division were used on the blackboard due to relative vertical displacements). Issuing warnings when either are used could certainly be entirely reasonable. 

08232021, 06:41 PM
Post: #11




RE: Imaginary Matrix Division
Can we get B*inv(A) without evaluating inverse and multiply ?


08242021, 05:19 AM
Post: #12




RE: Imaginary Matrix Division
(08232021 06:41 PM)Albert Chan Wrote: Can we get B*inv(A) without evaluating inverse and multiply ? Code: TRANS Cheers, Werner 41CV†,42S,48GX,49G,DM42,DM41X,17BII,15CE 

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