Introduced to in Math 115 [! Definition 3.2.2 Matrix-Vector Product] Let A = [] and = . Then the vector A is defined A = [! Matrix Equality Theorem] Let A, B . If A = B for every , then A = B [! Properties of Matrix Vector Product] Let A, B and c Then a) A() = b) A(c) = c(A) = (cA) c) (A + B) = A The n x n identity matrix, denoted by I (or I or just I if the size is clear) is the square matrix of size n n with (I) = 1 for i = 1, 2, , n and zeros elsewhere