Size is the number of row or column of a square matrix
(<=> (Size ?M) (And (Square-Matrix ?M) (= ?N (Row-Dimension ?M))))
(=> (Size $X $Y) (Square-Matrix $X)) (=> (= (Size ?M) ?N) (= ?N (Row-Dimension ?M))) (=> (= (Size ?M) ?N) (Square-Matrix ?M)) (=> (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)))))) (=> (= (Cofactor ?M ?I ?J) ?Cof) (< 1 (Size ?M)))