Question about the determinant of an upper triangular matrix Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)Getting the determinant value of the original matrix from its upper triangular matrixHow is diagonal matrices a subspace of upper triangular matrices?Upper Triangular Matrix DefinitionTransforming a matrix to upper triangular formWhat is the transformation matrix “by definition”?How to derive the Vandermonde Determinant?Various matrix manipulations effect on determinantDeterminant of Partitioned Upper Triangular MatrixHow would I answer the following question about the determinant of a matrix?Determinant of Triangular Matrix

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Question about the determinant of an upper triangular matrix



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)Getting the determinant value of the original matrix from its upper triangular matrixHow is diagonal matrices a subspace of upper triangular matrices?Upper Triangular Matrix DefinitionTransforming a matrix to upper triangular formWhat is the transformation matrix “by definition”?How to derive the Vandermonde Determinant?Various matrix manipulations effect on determinantDeterminant of Partitioned Upper Triangular MatrixHow would I answer the following question about the determinant of a matrix?Determinant of Triangular Matrix










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I was watching an online lecture on the properties of determinants and at 27:00 in this lecture: https://www.youtube.com/watch?v=srxexLishgY&t=4s, the professor did a step which I don't understand.



If $A = beginpmatrixd1 & 0 & 0\ 0 & d2 & 0\ 0 & 0 & d3endpmatrix $, then according to the lecturer, $A=d1 *d2 *d3 beginpmatrix1 & 0 & 0\ 0 & 1 & 0\ 0 & 0 & 1endpmatrix$, this was then used to show that the determinant of an upper triangular matrix can be written as the product of the leading diagonal
. However I thought if a matrix is multiplied by a number, all elements of the matrix are multiplied by it. Is this just wrong?










share|cite|improve this question









$endgroup$
















    1












    $begingroup$


    I was watching an online lecture on the properties of determinants and at 27:00 in this lecture: https://www.youtube.com/watch?v=srxexLishgY&t=4s, the professor did a step which I don't understand.



    If $A = beginpmatrixd1 & 0 & 0\ 0 & d2 & 0\ 0 & 0 & d3endpmatrix $, then according to the lecturer, $A=d1 *d2 *d3 beginpmatrix1 & 0 & 0\ 0 & 1 & 0\ 0 & 0 & 1endpmatrix$, this was then used to show that the determinant of an upper triangular matrix can be written as the product of the leading diagonal
    . However I thought if a matrix is multiplied by a number, all elements of the matrix are multiplied by it. Is this just wrong?










    share|cite|improve this question









    $endgroup$














      1












      1








      1


      1



      $begingroup$


      I was watching an online lecture on the properties of determinants and at 27:00 in this lecture: https://www.youtube.com/watch?v=srxexLishgY&t=4s, the professor did a step which I don't understand.



      If $A = beginpmatrixd1 & 0 & 0\ 0 & d2 & 0\ 0 & 0 & d3endpmatrix $, then according to the lecturer, $A=d1 *d2 *d3 beginpmatrix1 & 0 & 0\ 0 & 1 & 0\ 0 & 0 & 1endpmatrix$, this was then used to show that the determinant of an upper triangular matrix can be written as the product of the leading diagonal
      . However I thought if a matrix is multiplied by a number, all elements of the matrix are multiplied by it. Is this just wrong?










      share|cite|improve this question









      $endgroup$




      I was watching an online lecture on the properties of determinants and at 27:00 in this lecture: https://www.youtube.com/watch?v=srxexLishgY&t=4s, the professor did a step which I don't understand.



      If $A = beginpmatrixd1 & 0 & 0\ 0 & d2 & 0\ 0 & 0 & d3endpmatrix $, then according to the lecturer, $A=d1 *d2 *d3 beginpmatrix1 & 0 & 0\ 0 & 1 & 0\ 0 & 0 & 1endpmatrix$, this was then used to show that the determinant of an upper triangular matrix can be written as the product of the leading diagonal
      . However I thought if a matrix is multiplied by a number, all elements of the matrix are multiplied by it. Is this just wrong?







      linear-algebra matrices determinant






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      share|cite|improve this question










      asked Apr 2 at 16:37









      Vishal JainVishal Jain

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          $begingroup$

          you are right about multiplying a matrix by a constant.
          The professor in the video is also right, because he is calculating the determinant of the matrix.






          share|cite|improve this answer









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            $begingroup$

            you are right about multiplying a matrix by a constant.
            The professor in the video is also right, because he is calculating the determinant of the matrix.






            share|cite|improve this answer









            $endgroup$

















              0












              $begingroup$

              you are right about multiplying a matrix by a constant.
              The professor in the video is also right, because he is calculating the determinant of the matrix.






              share|cite|improve this answer









              $endgroup$















                0












                0








                0





                $begingroup$

                you are right about multiplying a matrix by a constant.
                The professor in the video is also right, because he is calculating the determinant of the matrix.






                share|cite|improve this answer









                $endgroup$



                you are right about multiplying a matrix by a constant.
                The professor in the video is also right, because he is calculating the determinant of the matrix.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Apr 2 at 16:40









                MoonKnightMoonKnight

                1,673611




                1,673611



























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