cos ⁡ ⁡ ( θ θ ∓ ∓ α α ) = A + B cos ⁡ ⁡ α α a ± ± C sin ⁡ ⁡ ( θ θ ∓ ∓ α α ) ( 1 + cos ⁡ ⁡ θ θ ) 2 ( sin ⁡ ⁡ α α ( 2 + cos ⁡ ⁡ α α ) ( 1 + cos ⁡ ⁡ α α ) 2 ∓ ∓ sin ⁡ ⁡ θ θ ( 2 + cos ⁡ ⁡ θ θ ) ( 1 + cos ⁡ ⁡ θ θ ) 2 )