1. Suppose that C is the top-half of the circle x + y = 2ax, (a > 0) oriented in the counterclockwise direction. Let F be a force field that has constant magnitude b and always directed from (x, y) toward the origin. By using the unit tangent vector T at (x, y), prove that the work done by the force F on a particle that moves along C is [F F.Tds 2ab. =