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If A is a symmetric matrix, B is a skew-...

If A is a symmetric matrix, B is a skew-symmetric matrix, `A+B` is nonsingular and `C=(A+B)^(-1) (A-B)`, then prove that
(i) `C^(T) (A+B) C=A+B` (ii) `C^(T) (A-B)C=A-B`
(iii) `C^(T)AC=A`

A

`A + B`

B

`A-B`

C

A

D

B

Text Solution

Verified by Experts

The correct Answer is:
C
Given, `A^(T) = A, B^(T) = -B, det (A+ B) ne 0`
and `C = (A + B)^(-1) (A-B)`
`rArr (A + B) C = A - B` ...(i)
Also, ` (A + B) ^(T)= A - B` ...(ii)
and ` (A - B) ^(T)= A + B` ...(iii)
`C^(T) AC = C^(T)((A+B +A-B)/2) C`
`= 1/2 C^(T) (A + B) C+ 1/2 C^(T) (A-B) C`
`= 1/2 (A + B) + 1/2 (A-B) `
`=A`
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