d″ = 5√ (32Q2 / gπ2i) 5√ ζ′ = 0.6319 5√ (Q2/i) 5√ ζ′.

(c) Equation 7 may be put in the form

d = 5√ (32αQ2 / gπ2i) 5√ (1 + 1/12d).

(9)

Expanding the term in brackets,

5√ (1 + 1/12d) = 1 + 1/60d − 1/1800d2 ...

Neglecting the terms after the second,

d = 5√ (32α / gπ2) 5√ (Q2/i) · {1 + 1/60d} = 5√ (32α / gπ2) 5√ (Q2/i) + 0.01667;

(9a)

and