(2)

if OD is the semi-diameter conjugate to OP, and r1, r2 the focal distances,

r1, r2 = c (ch η ± cos ξ);

(3)

r2 = x2 + y2 = c2 (ch2 η − sin2 ξ)

= ½c2 (ch 2η + cos 2ξ).

(4)

Consider the streaming motion given by

w = m ch (ζ − γ), γ = α + βi,

(5)