Between a fp, fa, k, 1, P, of some days - possibly weeks - the ova of the second Aplysia commence to descend the hermaphrodite duct; they become en FIG.
P is the position of the planet at any time, and we call r the radius vector FP. The angle AFP between the pericentre and the position P of the planet is the anomaly called v.
By Kepler's second law the radius vector, FP, sweeps over equal areas in equal times.
Since the area of the triangle FPP' is one half the product of FP into the perpendicular p from P on FP', it follows that if these perpendiculars were equal all round the orbit, the areas described during the infinitesimal time would be smallest at the pericentre and continually increase during the passage of the body to B.