Simple Matrices proof using Mathematica help

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SUMMARY

The discussion focuses on proving the matrix identity (AB)-1 = B-1A-1 using Mathematica. The user successfully verified the transpose identity but encountered issues with the inverse identity, where Mathematica returned expanded matrices instead of a boolean result. The problem stems from the syntax used in the inverse function, specifically the need for proper multiplication notation. Rounding errors in matrix calculations also contribute to discrepancies in results.

PREREQUISITES
  • Understanding of matrix operations, specifically inverses and transposes.
  • Familiarity with Mathematica syntax and functions.
  • Knowledge of 3x3 matrices and their properties.
  • Basic concepts of numerical precision and rounding in computational mathematics.
NEXT STEPS
  • Review Mathematica documentation on the Inverse function for proper usage.
  • Learn about matrix multiplication syntax in Mathematica.
  • Explore numerical precision techniques to handle rounding errors in matrix calculations.
  • Study proofs of matrix identities to deepen understanding of linear algebra concepts.
USEFUL FOR

Students studying linear algebra, Mathematica users seeking to perform matrix operations, and anyone interested in understanding matrix identities and their proofs.

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Simple Matrices proof using Mathematica help!

Homework Statement



Hey guys, I'm trying to prove that

(AB)-1 = B-1 A-1
and also the one that looks the same but is with transpose of the matrices

making A and B arbitrary 3x3 matrices. I made

A = {{a_1,a_2,a_3}...}
B = {{b_1,b_2,b_3}...}

and I was able to prove the Transpose one by typing "Transpose[A B] == Transpose * Transpose[A] " and it spit out the word "True"

However, when I write "Inverse[A B] == Inverse Inverse[A] ", it does not spit out the word true, rather it spits back out the matrices expanded. Does anyone know how to tweak it so that it'll spit out either the words true or false? Thanks


Homework Equations





The Attempt at a Solution

 
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making A and B arbitrary 3x3 matrices.
... and checking that the inverse exists?
when I write "Inverse[A B] == Inverse Inverse[A] ", it does not spit out the word true
check syntax - did you write the above or did you write:

Inverse[A B] == Inverse*Inverse[A]

(I can't remember if it matters)

I find that the inverse function does some rounding off, and the rounding is different if I do inverse[A*B] and when I do inverse[A]*inverse, so whenever I do Inverse[A*B] == Inverse*Inverse[A] it returns "false".
 
Last edited:

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