Timeline for Proving that Matrix is a Unit [duplicate]
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 23, 2018 at 21:52 | vote | accept | dmsj djsl | ||
| Oct 18, 2018 at 1:56 | history | closed | Viktor Vaughn CommunityBot | Duplicate of If $AB = I$ then $BA = I$ | |
| Oct 18, 2018 at 0:35 | review | Close votes | |||
| Oct 18, 2018 at 2:00 | |||||
| Oct 18, 2018 at 0:21 | comment | added | Viktor Vaughn | Some more duplicates: 1, 2. | |
| Oct 18, 2018 at 0:18 | comment | added | Viktor Vaughn | Did you first search to see if this question had been asked before? This is a duplicate of one of the most famous questions on this site. | |
| Oct 17, 2018 at 22:57 | answer | added | David Holden | timeline score: 1 | |
| Oct 17, 2018 at 22:33 | comment | added | user24142 | @rschweib its a humourous meme, with the epithet originally applied to David Morgan-Hewitt. | |
| Oct 17, 2018 at 22:28 | history | edited | dmsj djsl | CC BY-SA 4.0 | deleted 2 characters in body |
| Oct 17, 2018 at 22:20 | comment | added | rschwieb | @darijgrinberg if that is the case, then the “only when” is a mistake. It seems to me that is the same as “only if” which is the opposite direction. | |
| Oct 17, 2018 at 22:11 | comment | added | Joel Pereira | Recall that matrix multiplication corresponds to a composition of linear transformations. Since the identity is an isomorphism, and AB = I, that says that AB is injective and surjective. What can be said about A and B separately if AB is injective and surjective? Note also that the same thing can be said for BA = I, so anything that is true for A will be true for B. | |
| Oct 17, 2018 at 22:09 | comment | added | darij grinberg | You need to prove that if you have $AB = I$ or $BA = I$, then you have $AB = BA = I$. This is what the hint can help you with. | |
| Oct 17, 2018 at 22:07 | comment | added | rschwieb | @DaveBensonPhillips what’s an absolute unit? | |
| Oct 17, 2018 at 22:07 | comment | added | rschwieb | I don’t understand.... what is your definition of a unit of not the second thing? | |
| Oct 17, 2018 at 22:01 | comment | added | DaveBensonPhillips | That matrix is an absolute unit | |
| Oct 17, 2018 at 21:59 | history | asked | dmsj djsl | CC BY-SA 4.0 |