Write a brief review of integrals in spherical polar coordinates
∫ 0 ∞ ∫ 0 π ∫ 0 2 π e − r r d r d θ d ϕ {\displaystyle \int _{0}^{\infty }\int _{0}^{\pi }\int _{0}^{2\pi }e^{-r}r~{\textrm {d}}r~{\textrm {d}}\theta ~{\textrm {d}}\phi }
