Розрахунок: zwqSoB - 1
tan(φ) =
tan(φ) = $$tan(\phi)$$ = $$\frac{X_{L}-X_{C}}{R}$$ 
tan(φ) = - $$tan(\phi)$$ = $$\frac{X_{L}}{R}-\frac{X_{C}}{R}$$ 
φ = arctan(( - ))$$\phi$$ = $$arctan((\frac{X_{L}}{R}-\frac{X_{C}}{R}))$$ 
φ = arctan( - )$$\phi$$ = $$arctan(\frac{X_{L}}{R}-\frac{X_{C}}{R})$$ 