Orthonormal Basis

Let v1, v2, v3 be vectors in C^3, and A be the 3x3 matrix whose first column is v1,
second column is v 2, and third column is v3 . Prove that (v1, v2, v3 ) is an
orthonormal basis for C^3 if and only if A^-1= (A bar)^ T, where the bar denotes
complex conjugate, and the T denotes transpose, i.e., replacing the rows by the columns and vice versa.
Example:
If A = (1 i 2- i
3 + i 0 2i
1 1 2 + 2i ),

(A bar)^ T = (1 3-i 1
-i 0 1
2 + i -2i 2-2i)