Proving transpose(AB)=transpose(B)*tranpose(A) Help Needed

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Discussion Overview

The discussion revolves around proving the property of matrix transposition, specifically that transpose(AB) equals transpose(B) times transpose(A). It includes inquiries about definitions, approaches to proof, and related concepts in linear algebra.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks help to prove the property of matrix transposition for the product of two matrices.
  • Another participant questions the definition of "transpose," prompting a clarification about switching subscripts and interchanging rows and columns.
  • A suggestion is made to write out the summation for the ij-th entry of both sides to clarify the proof.
  • A participant notes that the definition of transpose applies to non-square matrices and discusses the implications for matrix multiplication.
  • One participant introduces the concept of induced maps on dual spaces, although this is not familiar to all contributors.
  • A separate inquiry is raised regarding proving the determinant of a matrix and its transpose using Laplace's expansion and the property of determinants for products of matrices.
  • Another participant suggests performing matrix multiplication and transposition for arbitrary matrices to demonstrate the property.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and familiarity with the concepts involved. There is no consensus on a specific approach to the proof, and multiple viewpoints and methods are presented without resolution.

Contextual Notes

Some participants may lack familiarity with advanced concepts like induced maps, which could limit their ability to engage fully with the discussion. There are also unresolved mathematical steps and assumptions regarding matrix dimensions and properties.

Who May Find This Useful

This discussion may be useful for students in introductory linear algebra courses or those interested in understanding properties of matrix operations and transpositions.

torquerotates
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I need help on the tranpose of a multiple of a matrix.

I need to prove: transpose(AB)=transpose(B)*tranpose(A)

Any Ideas?
 
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What is the definition of "transpose"?
 
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Well, from what I know, I just switch the subscripts and interchange rows and columns. So if A=a(ij) then, transpose(A)=a(ji)
 
I just don't know where to go from there
 
Did you try writing out the summation for the ij-th entry of both sides? I think it should be clear once you do that.
 
Recall that "transpose" is not only defined for square matrices. If A is an n by m matrix and B is an m by p matrix, so that you can multiply them, then AT is an m by n matrix and BT is a p by m matrix. If n is not equal to p, you can't multiply ATBT. But you can multiply BTAT.
 
if you know what it means in terms of being the induced map, namely composition, on dual spaces, the result is just the obvious fact that f*g*(h) = f*(g*h) = f*(hog) =
hogof = (gof)*(h) = (gf)*(h), so (gf)* = f*g*.
 
Well, I'm only taking an intro to linear algebra course. So I've never heard of an induced map.
 
How do you go about proving that the determinant of a nxn matrix A is equal to the determinant of the transpose of said matrix A using Laplace's expansion?

How can you use Det(AB) =Det A x det B to help with this?
 
  • #10
what you need to do is to do a matrix multiplication for an abitrary matrix A and matrix B, I should say a transpose multiplication of matrix A and then transpose of matrix B. Then find the multiplication of matrix AB and find the transpose of that. It should be the same and that should do it.
 

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