| λ − μ | = | 1 + z | , | μ − ν | = | 1 − z |
| λ − ν | 2 | λ − ν | 2 |
(39)
with z = cos θ, θ denoting the angle between the generating lines through H; and with OC = δ, OC′ = δ′, the length k has been chosen so that in the preceding equations
δ/k = G/2An, δ′/k = G′/2An;
(40)
and δ, δ′, k may replace G, G′, 2An; then
| 2Z | = | 1 | ( | dθ | ) | 2 | = | 4KH2 | , |
| 1 − z2 | n2 | dt | k2 |
(41)
while from (33-39)
| 2Z | = | 4 (α2 + μ) (β2 + μ) μ | , |
| 1 − z2 | k2 (μ − λ) (μ − ν) |