




1. With the field given by (z  x^{2})i  yj + sin(x)k, where are there sources and where sinks?
Since the divergence is 1  2x, it is positive (points are sources of arrows)
when x < 1/2
and negative (all points are sinks) when x > 1/2.
2. Where are sources and sinks for the field r^{3}?
This field has a source at the origin and arrows point radially outward; there
are no finite sinks; the arrows, if connected into lines, all go out to infinity.
Notice that the origin is definitely a source of arrows.