Let r = (x^2 + y^2)^1/2 and consider the vector field f = r^a(-yi + xj), where r 0 and a is a constant. f has no z-component and is independent of z. find curl r^a(-yi + and show that it can be written in the form curl f = r^a k, where a =, for any constant a. using your answer to part (a), find the direction of the curl of the vector fields with each of the following values of.4 (enter your answer as a unit vector in the direction of the curl): a = -5 direction = a = 2 direction = for each values of.4 in part (b), what (if anything) does your answer to part (b) tell you about the sign of the circulation around a small circle oriented counterclockwise when viewed from above, and centered at (1, 1, 1)? if a = -5, the circulation is if a = 2, the circulation is