Let R and C be as in Green??s theorem, r' a unit tngent vector, and n the outer unit normal vector of C (Fig. 238 in Example 4) show that (1) may be written where k is a unit vector perpendicular to the xy-plane. Verify (11) and (12) for F = [7x, ?? 3y] and C the circle x2 + y2 = 4 as well as for an example of your ownchoice?

(11) (12) [f div F dx dy = f F-n ds R [[(curt F) k dx dy = f F-r' ds R