(3) Given the triangle with vertices A(-1, 2, -1), B(-1, 3, 1) and C(2, 1, 1). Find (a) (5 points) the length of the side AB, (b) (5 points) the measure of angle B. You may leave your answer in arccos format. (4) (2 points, bonus) Given two unit vectors u and v such that Ju + v = 2, show that u = v. (5) (2 points, bonus) Determine whether the statement is true or false. If it is true, prove it. If it is false, give an example that shows it is false. If u . v = u . w and u # 0, then v = w