Question

Let A be an 80  80 matrix. Prove that if AA^T = I, then det(A) 1 = or -1.

Answer 1

.

Answer 2

is that 80x80 matrix ??

Answer 3

det(AB) = det(A)det(B)
det(A^T) = det(A)

put this all together :

det(AA^T) = det(A)det(A^T) = det(A)det(A) = det(I)
det(A)^2 = 1
det(A) = 1,-1

Answer 4

yes, 80x80

Answer 5

Coolsector's method works for any nxn

Answer 6

zarkon...i posted question for u again