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I'm trying to express

$$A = \left[ \begin{array} { r r r } { 2 } & { - 2 } & { - 4 } \\ { - 1 } & { 3 } & { 4 } \\ { 1 } & { - 2 } & { - 3 } \end{array} \right]$$

as the sum of a symmetric and a skew symmetric matrix.

So far I have tried this:

converting into transpose

$A ^ { \prime } = \left[ \begin{array} { c c c } { 2 } & { - 1 } & { 1 } \\ { - 2 } & { 3 } & { 4 } \\ { - 4 } & { 4 } & { - 3 } \end{array} \right]$

well this dont seem to be symmteric matrix according to me. are there steps to be taken.

and for skew symmteric matrix i tried to do like this

transpose of equation $A ^ { \prime } = \left[ \begin{array} { c c c } { 2 } & { - 1 } & { 1 } \\ { - 2 } & { 3 } & { 4 } \\ { - 4 } & { 4 } & { - 3 } \end{array} \right]$

took minus as common $A ^ { \prime } = \left[ \begin{array} { c c c } { - 2 } & { 1 } & { - 1 } \\ { 2 } & { - 3 } & { 2 } \\ { 4 } & { - 4 } & { 3 } \end{array} \right]$

can you guide me how to proceed with them

user
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Gaurav Singh
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  • Your question is unclear. Do you want to ask how to find matrices $B$ and $C$ such that $B$ is symmetric and $C$ is skew-symmetric with $A=B+C$? – Jan Sep 05 '18 at 12:04
  • not trying to find but trying to express as symmteric and skew symmteric matrix – Gaurav Singh Sep 05 '18 at 12:06

1 Answers1

3

HINT

Recall that for any square matrix $A$

$$A=\frac{A+A^T}{2}+\frac{A-A^T}{2}$$

and

$$\left(\frac{A+A^T}{2}\right)^T=\frac{A^T+A}{2}=\frac{A+A^T}{2}$$

$$\left(\frac{A-A^T}{2}\right)^T=\frac{A^T-A}{2}=-\frac{A-A^T}{2}$$

user
  • 162,563
  • It took me less than one minute to find a duplicate. Did you really think this has not been asked and answered before? – Martin R Sep 05 '18 at 17:03
  • @MartinR I simply didn't check for that. I also gave related answer sometimes but in other context. Anyway I can't see any problem since I see that the OP will be closed and linked to the duplicate for future reference. And also "repetita juvant" sometimes. Bye – user Sep 05 '18 at 17:12