11 1f A, B are two n x n symmetric matrices, then AB is an n x n symmetric matrix. 12 The union V U W of any two linear sub-space V, W of R^n is not a linear space. 13 If two square matrices A and B have the same characteristic polynomials, then trA = tr(B). 14 For any orthogonal matrix A, the matrix (A - A^-1) is skew symmetric. 15 For any 2 x 2 orthogonal matrix A, the linear transformation T : R^2 R^2 defined by vector x A vector x is a rotation. Solution 11) False AB is a symmentric matrix when A and B are symmetric iff A and B commute 12) True say V is a points on x-axis and w is a points of y-axis then their sum is not in the union hence it is not closed under addition hence not a subspace 13) False for 2- square matrix characterstic polynomial is given by t^2 + tr(A) + det(A) so, determinent can be different 14) True 15) True.