In the Faddeev-Popov procedure one defines the Faddeev-Popov determinant through the formula $$\int {\mathcal{D}\alpha \ } \delta\big[G(A^\alpha)\big]\Delta[A]=1,\tag{1}$$ where $G(A^\alpha)$ is the gauge-fixing condition and $A^\alpha$ is the gauge field $A$ transformed by a finite gauge transfo...