44:25 "orthogonal matrices don't change the length of x" I guess he meant orthonormal. [Gilbert Strang uses orthogonal and orthonormal interchangeably]####[['orthonormal', 'Mathematical_Related_Concept', 'NEU'], ['Gilbert Strang', 'Instructor', 'NEU'], ['orthogonal', 'Mathematical_Related_Concept', 'NEU']]