Let f(x, y) = sin x sin y. (a) By visually examining the field F, guess where

Question:

Let f(x, y) = sin x sin y.
(a) By visually examining the field F, guess where div F is positive and where it is negative. Then calculate div F to check on your guesses.
(b) Calculate the flux of F across the boundary of S; then calculate it across the boundary of T = {(x, y)}; 0 ( x ( 3, 0 ( y ( 3}?