where S is the surface of the garden defined above and n is a unit normal to the surface S Evaluating this surface integral will measure the tendency for the air to circulate in the direction that Anna likes to walk around her garden Note that a negative value just means that she is walking into the breeze Hints An application of Stokes theorem suggests the answers in i and ii should be equal to each ther You may use the integrals sin u du u 2 1 4 sin 2u sinu sin u cos u du 1 4 cos2u Further hints on next page