15. If u has magnitude 20 and points at an angle 9, measured counter-clockwise from the positive x-direction (this is called a direction angle), find a general formula for the components of in terms of the angle 0. 16. Calculate the magnitude and the direction angle (in radians) for the vector = (3,-33). 17. Find a unit vector (that's a vector of magnitude 1) that points in the same direction as = (-6,8). 18. Find a vector (in component form) so that ||| = 392 and when drawn in standard position makes a 117 angle with the positive x-axis. 19. Calculate the magnitude and direction angle (in degrees) for the vector 7= (-7,3).