where X3 is a quartic function of x3, and thus t is given by an elliptic integral of the first kind; and by inversion x3 is in elliptic function of the time t. Now

(x1 − x2i) (y1 + y2i) = x1y1 + x2y2 + i (x1y2 − x2y1) = FG − xy3y3 + i √ X3,

(9)

y1 + y2i= FG − x3y3 + i √ X3,
x1 + x2i x12 + x22

(10)

d(x1 + x2i) = −i [ (q′ − q) x3 + r′y3 ] + irx3 (y1 + y2i),
dt

(11)

dlog (x1 + x2i) = −(q′ − q) x3 − r′y3 + rx3 FG − x3y3 + i √ X3,
dti F2 − x32

(12)

dlog √ x1 + x2i= −(q′ − q) x3 − (r′ − r) y3 − Fr Fy3 − Gx3,
dti x1 − x2iF2 − x32