QUESTION 4 A square matrix has an inverse if and only if It is not the identity It is a rotation matrix Its determinant is not zero It has a homogeneous representation QUESTION 5 The origin is The unique matrix M such that Mx = x for every x. The unique 0-dimensional vector One of the standard basis vectors The vector with all zeros QUESTION 6 The standard basis vectors are The set of vectors used in homogeneous respresentations of matrices O The set of vectors that have a 1 in one position and O's elsewhere The columns of a given rotation matrix The unique set of vectors that are linear combinations of each other