1, different meanings: cross product | c | =| a× b | | a | | b | sin, c is a vector, not a scalar, and vector c is perpendicular to A and B, which satisfies the right-hand rule.
2. The nature is different: AB represents the multiplication of two matrices A and B, provided that the number of columns of A is equal to the number of rows of B, and it is still a matrix after multiplication. |AB| represents the determinant of the product of two matrices A and B (which is a new matrix) and is a number. |AB|=|A||B|。
concept
Linear algebra is a branch of algebra, which mainly deals with linear relations. Linear relationship means that the relationship between mathematical objects is expressed in linear form. For example, in analytic geometry, the equation of a straight line on the plane is a binary linear equation; The equation of spatial plane is a ternary linear equation, and the spatial straight line is regarded as the intersection of two planes, which is represented by an equation group composed of two ternary linear equations. A linear equation with n unknowns is called a linear equation.