d[sigma] de
-------- = [rho], -- = [rho]([chi]' - 4[pi][rho][theta](0)) + 4[pi][rho]^2[theta](c).
dc dc
Hence the surface-tension
_
de / / c \
T = e - [sigma] -------- = 4[pi][rho]^2 ( | [theta](z)dz - c[theta](c) ).
d[sigma] \ _/0 /
Integrating the first term within brackets by parts, it becomes
_
/ c d[theta]
c[theta](c) - 0[theta](0) - | z -------- dz.
_/0 dz