Linear Algebra help!

[hayood]

Prove that a square matrix A is invertible if and only if Atranspose A is invertible.

i dont know how to prove it. if anyone can offer some help please let me know
thanks

 

[tutor_joel]

I believe that A is invertible iff det(A) is not zero and iff det(A^TA) is not zero. Does that ring a bell?

det being the determinant

 

[hayood]

ya solved it thanks a lot