1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding 2 2x2 matrices resulting in -1

  1. Feb 2, 2009 #1
    1. The problem statement, all variables and given/known data
    Find two different 2×2 matrices (other than ±I) such that A.AT = I.

    Definition: I is referring to i^2=-1 axion
    AT=Transpose of A

    2. Relevant equations

    3. The attempt at a solution
    Trying to make matrices on paper so that A times the transpose of A gives me -1 in all rows and columns.
  2. jcsd
  3. Feb 2, 2009 #2
    Have you tried just writing out a matrix A with enries a,b,c,d, what would A^T look like then? Then multiply it out and set equal to I?

    I'm not sure what you mean by "I is refering to i^2 = -1". I thought by "I" you meant the identity matrix?
  4. Feb 2, 2009 #3
    No, there's an axion in mathematics apparently where the variable "i squared" (i^2) equals -1. The reason I wrote a Capital I is because I'm working with a program called Maple. It's the same thing, but in the two matrices that I have to find, I can't use the -1 axion.

    Sorry for the confusion.
  5. Feb 2, 2009 #4
    Yes but i^2 = -1 is an imaginary/complex number. You are working with matrices where I refers to the identity matrix.
  6. Feb 2, 2009 #5
    ......well I feel stupid as all...

    lol thx for clearing that up. ^^;
  7. Feb 2, 2009 #6


    Staff: Mentor

    No, i^2 is not imaginary. i is, though:biggrin:
  8. Feb 2, 2009 #7
    Haha, yes.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Finding 2 2x2 matrices resulting in -1