Graph the given velocity field v of a fluid flow in a square centered at the origin with sides parallel to the coordinate axes. Recall that the divergence measures outflow minus inflow. By looking at the flow near the sides of the square, can you see whether div v must be positive or negative or may perhaps be zero? Then calculate div v. First do the given flows and then do some of your own. Enjoy it.

(a) v = i 

(b) v = xi

(c) v = xi - yj