Биенето, кредитната интерференция

f(t) = cos[t(Ω₁ + Ω₂)/2] cos[t(Ω₁ - Ω₂)/2]; 0 < Ω₁ ≈ Ω₂ > 0

 
cosA1 + cosA2 = 2 cos[(A1 + A2)/2] cos[(A1 - A2)/2] = (2/1 = 2) {"1"±"2"}
 
(cosA1 + cosA2) + cosA3 = 2 cos[(A1 + A2)/2] cos[(A1 - A2)/2] + cosA3
(cosA1 + cosA3) + cosA2 = 2 cos[(A1 + A3)/2] cos[(A1 - A3)/2] + cosA2
(cosA2 + cosA3) + cosA1 = 2 cos[(A2 + A3)/2] cos[(A2 - A3)/2] + cosA1
----------
cosA1 + cosA2 + cosA3 = cos[(A1 + A2)/2] cos[(A1 - A2)/2]
                                        + cos[(A1 + A3)/2] cos[(A1 - A3)/2]
                                        + cos[(A2 + A3)/2] cos[(A2 - A3)/2]
                                        = (3/3 = 1) ({"1"±"2"} + {"1"±"3"} +
                                                        + {"2"±"3"})
 
(cosA1 + cosA2 + cosA3) + cosA4 = {"1"±"2"} + {"1"±"3"} + {"2"±"3"} + cosA4
(cosA1 + cosA2 + cosA4) + cosA3 = {"1"±"2"} + {"1"±"4"} + {"2"±"4"} + cosA3
(cosA1 + cosA3 + cosA4) + cosA2 = {"1"±"3"} + {"1"±"4"} + {"3"±"4"} + cosA2
(cosA2 + cosA3 + cosA4) + cosA1 = {"2"±"3"} + {"2"±"4"} + {"3"±"4"} + cosA1
----------
cosA1 + cosA2 + cosA3 + cosA4 = (4/6 = 2/3) ({"1"±"2"} + {"1"±"3"} + {"1"±"4"}
                                                                          + {"2"±"3"} + {"2"±"4"}
                                                                          + {"3"±"4"})
 
...
 
A = tΩ:
∑ _{k = 1}^{n ≥ 2} cos(tΩ_k):
F(t) = (n/C_n²) ∑ _{i = 1}^n-1 ∑ _{k = 1}ⁿ cos[t(Ω_i + Ω_k>i)/2] cos[t(Ω_i - Ω_k>i)/2]
       = [2 / (n - 1)] ∑ _{i = 1}^n-1 ∑ _{k = 1}ⁿ cos[t(Ω_i + Ω_k>i)/2] cos[t(Ω_i - Ω_k>i)/2];
          0 < Ω_i ≈ Ω_k>i > 0; n = 2, 3, 4, ...
 
n = 5 → (1/2) ({"1"±"2"} + {"1"±"3"} + {"1"±"4"} + {"1"±"5"}
                     + {"2"±"3"} + {"2"±"4"} + {"2"±"5"}
                     + {"3"±"4"} + {"3"±"5"}
                     + {"4"±"5"})

...