The 1 -form
\psi =(udv-vdu)/(u^(2)+v^(2))
is well-defined on the plane
R^(2)
with the origin
0
removed. Show: (a)
\psi
is closed but not exact on
R^(2)-0
. (Hint: Integrate around the unit circle and use Ex. 3.) (b) The restriction of
\psi
to, say, the right half-plane
u>0
is exact.