an identity matrix d)is a diagonal matrix with all diagonal terms being unity.(单位矩阵) 10 01 2021/1/21
2021/1/21 11 cxt ❖ An identity matrix (I) is a diagonal matrix with all diagonal terms being unity.（单位矩阵）
令 An inverse matrix(逆矩阵) To a square matrix a, if a square matrix B exists and ab=ba l. then b is the inverse matrix of A(or a is the inverse matrix of B) 2021/1/21
2021/1/21 12 cxt ❖ An inverse matrix （逆矩阵） To a square matrix A, if a square matrix B exists and AB=BA=I. Then B is the inverse matrix of A(or A is the inverse matrix of B)
The trace of a matrix is the sum of the diagonal terms(矩阵的迹). This is only defined for square matrices 例:给定一个矩阵A, a b c d 令求矩阵A的迹? tr(A)=∑a=a+b i=1 2021/1/21 13
2021/1/21 13 cxt ❖ The trace of a matrix is the sum of the diagonal terms （矩阵的迹）. This is only defined for square matrices. ❖ 例：给定一个矩阵A， ❖ 求矩阵A的迹？ tr(A)= =a+b 1 ii p i a =
◆矩阵运算 (1) Matrix addition and subtraction(矩阵 加法和减法) 例: 964 B=25 813 A+B=711 A-B=31 610 2021/1/21
2021/1/21 14 cxt ❖ 矩阵运算 （1）Matrix Addition and Subtraction（矩阵 加法和减法） 例：
令续例1: 令欲求每人、每科两次考试的总分数, 85+8880+83)(173163 4+B=90+9282+85182167|= 75+766+66)(151129 即把两个矩阵的对应元素相加。 Matrices with different dimensions cannot be added or subtracted.(只有当两个矩阵同行数、 同列数时,才能相加减。) 2021/1/21 15
2021/1/21 15 cxt ❖ 续例1： ❖ 欲求每人、每科两次考试的总分数， 即把两个矩阵的对应元素相加。 ❖ Matrices with different dimensions cannot be added or subtracted.（只有当两个矩阵同行数、 同列数时，才能相加减。）