Prove normal matrices are RPN (Range perpendicular to Null space) Matrices?












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For a normal matrix $A$, $A^* A = A A^*$ where $A^*$ is the conjugate transpose of $A$

Prove that for normal matrices
$$C(A) perp N(A)$$










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    $begingroup$


    For a normal matrix $A$, $A^* A = A A^*$ where $A^*$ is the conjugate transpose of $A$

    Prove that for normal matrices
    $$C(A) perp N(A)$$










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      For a normal matrix $A$, $A^* A = A A^*$ where $A^*$ is the conjugate transpose of $A$

      Prove that for normal matrices
      $$C(A) perp N(A)$$










      share|cite|improve this question









      $endgroup$




      For a normal matrix $A$, $A^* A = A A^*$ where $A^*$ is the conjugate transpose of $A$

      Prove that for normal matrices
      $$C(A) perp N(A)$$







      linear-algebra






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      asked Nov 27 '18 at 4:08









      Nagabhushan S NNagabhushan S N

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          I will use the language of linear transformations. We have $|A^{*}x|^{2}=langle A^{*}x, A^{*}xrangle =langle AA^{*}x, xrangle =langle A^{*}Ax, xrangle ==langle Ax, Axrangle =|Ax|^{2}$ which shows that for any $x$ in the null space of $A$ we also have $A^{*}x=0$. Now let $x$ be in the null space of $A$ and consider any vector $Ay$ in the range of $A$. We have $langle Ay, xrangle =langle y, A^{*}xrangle =langle y, 0rangle =0$.






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            $begingroup$

            I will use the language of linear transformations. We have $|A^{*}x|^{2}=langle A^{*}x, A^{*}xrangle =langle AA^{*}x, xrangle =langle A^{*}Ax, xrangle ==langle Ax, Axrangle =|Ax|^{2}$ which shows that for any $x$ in the null space of $A$ we also have $A^{*}x=0$. Now let $x$ be in the null space of $A$ and consider any vector $Ay$ in the range of $A$. We have $langle Ay, xrangle =langle y, A^{*}xrangle =langle y, 0rangle =0$.






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              $begingroup$

              I will use the language of linear transformations. We have $|A^{*}x|^{2}=langle A^{*}x, A^{*}xrangle =langle AA^{*}x, xrangle =langle A^{*}Ax, xrangle ==langle Ax, Axrangle =|Ax|^{2}$ which shows that for any $x$ in the null space of $A$ we also have $A^{*}x=0$. Now let $x$ be in the null space of $A$ and consider any vector $Ay$ in the range of $A$. We have $langle Ay, xrangle =langle y, A^{*}xrangle =langle y, 0rangle =0$.






              share|cite|improve this answer









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                $begingroup$

                I will use the language of linear transformations. We have $|A^{*}x|^{2}=langle A^{*}x, A^{*}xrangle =langle AA^{*}x, xrangle =langle A^{*}Ax, xrangle ==langle Ax, Axrangle =|Ax|^{2}$ which shows that for any $x$ in the null space of $A$ we also have $A^{*}x=0$. Now let $x$ be in the null space of $A$ and consider any vector $Ay$ in the range of $A$. We have $langle Ay, xrangle =langle y, A^{*}xrangle =langle y, 0rangle =0$.






                share|cite|improve this answer









                $endgroup$



                I will use the language of linear transformations. We have $|A^{*}x|^{2}=langle A^{*}x, A^{*}xrangle =langle AA^{*}x, xrangle =langle A^{*}Ax, xrangle ==langle Ax, Axrangle =|Ax|^{2}$ which shows that for any $x$ in the null space of $A$ we also have $A^{*}x=0$. Now let $x$ be in the null space of $A$ and consider any vector $Ay$ in the range of $A$. We have $langle Ay, xrangle =langle y, A^{*}xrangle =langle y, 0rangle =0$.







                share|cite|improve this answer












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                share|cite|improve this answer










                answered Nov 27 '18 at 6:08









                Kavi Rama MurthyKavi Rama Murthy

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                55.9k42158






























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