Function that returns the determinant of a matrix It has relevant informations such as if determinant = 0 the the matrix cannot be inverted
(=> (And (Square-Matrix ?M))
(= (Determinant ?M)
(Cond ((= 1 (Size ?M)) (Value ?M 1 1))
((< 1 (Size ?M))
(Summation (Lambda (?J)
(* (Value ?M 1 ?J)
(Cofactor ?M 1 ?J)))
1
(Size ?M))))))