If the matrix A is both symmetric and skew symmetric, then
Given A is both symmetric and skew symmetric matrix then, A = A’ and also A = -A’
⇒ A’ = -A’
⇒ 2A’ = 0
⇒ A’ = O
Clearly it is observed that transpose of A is a null matrix or zero matrix then matrix A must also be a zero matrix.
Hence A is a zero matrix.