\tan ϕ_{Σ} = \frac{E_{01} \sin ϕ_{1} + E_{02} \sin ϕ_{2}}{E_{01} \cos ϕ_{1} + E_{02} \cos ϕ_{2}}

${\tan \phi_\Sigma = \frac{E_{01} \sin \phi_1 + E_{02} \sin \phi_2}{E_{01} \cos \phi_1 + E_{02} \cos \phi_2}}$

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