and integrating

½CH2 = A2n2 (E − cos θ),

(6)

½OH2 = A2n2 (F − cos θ),

(7)

½C′H2 = A2n2 (D − cos θ),

(8)

where D, E, F are constants, connected by

F = E + G2/2A2n2 = D + G′2/2A2n2.

(9)