(b) (5 分) What is ds， where C is the arc of the helix x = cost， y = sint， z = t， which joins the points (1， 0， 0) and (-1， 0， π)?

(a) (5 分) Let be a force， calculate the work done in the displacement along the helix C: from A(2， 0， 0) to B(0， 2， 3π).

【試題 6】(20 分) Use Green's theorem to evaluate the line integral

where C is the boundary of the region defined by x = 0， y = 0， and x + y = 1.