symmetric matrix 的公式和例子 skew symmetric matrix 的公式和例子是什么啊 急

symmetric matrix:A(ij)=A(ji),or AT = A
skew symmetric:A(ij)= -A(ji),or AT = -A
Here,A(ij) is the element in ith row and jth column of matrix A.
AT is the transpose of matrix A.
e.g.A= [1 2 3]
[2 9 4]
[3 4 5] is symmetric.
A=[1 2 3]
[-2 9 -4]
[-3 4 5] is skew-symmetric.