  For a drop on an incline with small tilt angle or small Bond number, when the
contact line is a circle, we show that the retentive force factor is exactly
pi/2 at first order in the tilt angle or the Bond number. The retentive force
factor is the ratio between the weight component along the slope and a
capillary force defined as surface tension times radius of contact line times
difference of cosines of contact angles at the back and at the front of the
drop. The drop profile is computed exactly in the same approximation. These
results are compared with Surface Evolver results, showing a surprisingly large
range of applicability of first order approximations.
