Null matrix can be an idempotent matrix?

  • Thread starter gianeshwar
  • Start date
  • #1
222
12
Friends!
Is there anything wrong in the statement"A null matrix is idempotent".
 

Answers and Replies

  • #2
34,694
6,397
Friends!
Is there anything wrong in the statement"A null matrix is idempotent".
What do you think? How is the term "idempotent" defined?
 
  • #3
222
12
A square equal A. So if A is zero matrix then it satsfies this condition.
 
  • #4
34,694
6,397
A square equal A. So if A is zero matrix then it satsfies this condition.
Any square zero matrix A is idempotent, since A2 = A. So, in regard to your question in the first post, not all zero matrices are idempotent, since A2 might not be defined. For example,
$$A = \begin{bmatrix} 0 & 0 & 0 \\ 0 & 0 & 0\end{bmatrix}$$
 
  • #5
222
12
Thank You.Doubt had arisen while showing B square not equal to I to be not always true when given B equal I minus A and A is idempotent.
 
  • #6
34,694
6,397
Thank You.Doubt had arisen while showing B square not equal to I to be not always true when given B equal I minus A and A is idempotent.
I'm not sure what you're trying to say here. Writing an equation would make it clearer.

Are you saying that B = I - A, and A is idempotent? And you need to show that B2 ≠ I?

If so, that's easy to show -- just expand B2 = (I - A)2.
 
  • #7
222
12
I needed to show that( B squarenot equai to I) is not always true.
 
  • #8
34,694
6,397
I needed to show that( B squarenot equai to I) is not always true.
Like I said in my previous post, this is easy to do.

Also, please take some time to learn how to write proper math notation. To indicate the square of something, at the very least you can write B^2. Better yet, write the exponent as a superscript, like this: B2. The x2 icon in the menu bar can be used to write exponents of all kinds. The ##\Sigma## icon in the menu bar has many math symbols, such as ≠ and ∞ and many others.
 
  • #9
222
12
Thank You Mark44 for the valuable help and suggestions!
 
  • #10
34,694
6,397
Thank You Mark44 for the valuable help and suggestions!
You're welcome!
 

Related Threads on Null matrix can be an idempotent matrix?

  • Last Post
Replies
4
Views
1K
Replies
9
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
2
Views
4K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
18
Views
17K
  • Last Post
Replies
4
Views
5K
  • Last Post
Replies
7
Views
1K
Top