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Which of the following statement('s) is/are TRUE?

(A) Skew symmetric matrix of even order is always symmetric

(B) Skew symmetric matrix of odd order is non-singular

(C) Skew symmetric matrix of odd order is singular

(D) Skew symmetric matrix is always square matrix

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 2

A matrix is skew-symmetric if AT=−AA^T = -A.

This means all diagonal elements must be 0 (since aii=−aiia_{ii} = -a_{ii} only if aii=0a_{ii} = 0).


Statement (A): Skew symmetric matrix of even order is always symmetric

Skew-symmetric requires: AT=−AA^T = -A

Symmetric requires: AT=AA^T = A

These are opposite conditions. A matrix cannot satisfy both unless it is the zero matrix.

For a 2×22 \times 2 skew-symmetric matrix:

A=[02−20]A = \begin{bmatrix} 0 & 2 \\ -2 & 0 \end{bmatrix}

AT=[0−220]=−AA^T = \begin{bmatrix} 0 & -2 \\ 2 & 0 \end{bmatrix} = -A

Since A≠ATA \neq A^T, the matrix is not symmetric.

Statement (A) is FALSE.


Statement (C): Skew symmetric matrix of odd order is singular

For any skew-symmetric matrix AA:

det⁡(A)=det⁡(AT)\det(A) = \det(A^T)

det⁡(AT)=det⁡(−A)\det(A^T) = \det(-A)

det⁡(−A)=(−1)n×det⁡(A)\det(-A) = (-1)^n \times \det(A) where nn is the order

For odd order (n=1,3,5,...n = 1, 3, 5, ...):

det⁡(A)=(−1)n×det⁡(A)\det(A) = (-1)^n \times \det(A)

det⁡(A)=−det⁡(A)\det(A) = -\det(A)

2det⁡(A)=02\det(A) = 0

det⁡(A)=0\det(A) = 0

The matrix is singular.

Statement (C) is TRUE.


Statement (B): Skew symmetric matrix of odd order is non-singular

This is the opposite of statement (C).

Statement (B) is FALSE.


Statement (D): Skew symmetric matrix is always square matrix

For the condition AT=−AA^T = -A to be valid:

If AA is m×nm \times n, then ATA^T is n×mn \times m.

For AT=−AA^T = -A, both must have the same dimensions.

This requires m×n=n×mm \times n = n \times m, so m=nm = n.

The matrix must be square.

Statement (D) is TRUE.


Statements (C) and (D) are TRUE.

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