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Express the following matrices as the sum of a symmetric and a skew symmetric matrix: [351-1] - Mathematics

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Question

Express the following matrices as the sum of a symmetric and a skew symmetric matrix:

`[(3,5),(1,-1)]`

Sum
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Solution

to suppose, A = `[(3,5),(1, -1)],` A' =`[(3,1),(5, -1)]`

So, A `1/2` (A + A') + `1/2` (A - A')

Let, P = `1/2` (A + A') = `1/2 ([(3, 5),(1, -1)]) + ([(3, 1),(5, -1)])`

`= 1/2 [(3 + 3, 5 + 1), (1 + 5, -1 -1)]`

`= 1/2 [(6, 6), (6, -2)]`

`= [(3, 3), (3, -1)]`

and, `"P'" = [(3, 3), (3, -1)] = "P",`

Therefore, the matrix P is a symmetric matrix.

Then, Q = `1/2` (A - A') = `1/2  ([(3, 5),(1, -1)]) - ([(3, 1),(5, -1)])`

`= 1/2 [(3 - 3, 5 -1), (1 - 5, -1 + 1)]`

`= 1/2 [(0,4), (-4, 0)]`

`= [(0,2), (-2, 0)]`

and, Q' = `[(0,2), (-2, 0)]` = - Q,

Hence the matrix Q is a skew symmetric matrix.

So, A = P + Q

= `[(3, 3), (3, -1)] + [(0, -2),(-2, 0)]`

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Chapter 3: Matrices - Exercise 3.3 [Page 89]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 3 Matrices
Exercise 3.3 | Q 10.1 | Page 89

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