3) (From Hardcover Book, Marsden/Tromba, Vector Calculus, 6th ed., Section 1.5., # 7 or from your Ebook in the Supplementary Exercises for Section 11.7, #184) Let v, w ER". If v| = w|, show that v + w and v - w are orthogonal (perpendicular). 4) (From Hardcover Book, Marsden/Tromba, Vector Calculus, 6th ed., Section 1.5., # 24, or from your Ebook in the Supplementary Exercises for Section 11.7, #201) Find two 2x2 matrices A and B such that AB = 0 but BA * 0