It is
= B ( − σ cos ϕ + 1 − σ 2 sin 2 ϕ ) , {\displaystyle ={\mathfrak {B}}\left(-\sigma \ \cos \phi +{\sqrt {1-\sigma ^{2}\sin ^{2}\ \phi }}\right),}
from which the relations
cos ϕ = 1 − σ cos φ 1 + σ 2 − 2 σ cos φ {\displaystyle \cos \phi ={\frac {1-\sigma \ \cos \varphi }{\sqrt {1+\sigma ^{2}-2\sigma \ \cos \ \varphi }}}}
and
are given.
Thus it is
if we insert this into equation i = i 0 + p 1 c {\displaystyle i=i_{0}+p_{1}c} , then it follows
= i 0 cos ϕ + σ 1 − σ 2 sin 2 ϕ B ( 1 − σ 2 ) 1 − σ 2 sin 2 ϕ . {\displaystyle =i_{0}{\frac {\cos \phi +\sigma {\sqrt {1-\sigma ^{2}\sin ^{2}\phi }}}{{\mathfrak {B}}(1-\sigma ^{2}){\sqrt {1-\sigma ^{2}\sin ^{2}\phi }}}}.}
Quite similar it is given: