Invertible Matrix

det(A^T) = det (A) (transposing)

det(A^TA) = det(A^T)*det(A) = {det(A)}² >0

since det(A)≠0 as the matrix is invertible

@aditya, what if the matrix have imaginary terms?

then (det A)² can be negative ...?

johncenaiit
That is the question? if the elements from complex numbers
this will not excepted.

but complex number matrices are also invertible, if det≠0

so you must specify its a real matrix...