® A square matrix A is said to be singular or non-singular according as
|A| = 0 or |A| ≠ 0 ® If AB = BA = I, where B is square matrix, then B is called inverse of A Also A–1 = B or B–1 = A and hence (A–1)–1 = A ® A square matrix A has inverse if and only if A is non-singular