Solve ∫ _{r_{1}}^r_{2}1/r^2dr

$$\int _ { r _ { 1 } } ^ { r _ { 2 } } \frac { 1 } { r ^ { 2 } } d r$$

Evaluate

$$\left\{\begin{matrix}\infty,&\left(r_{1}>0\text{ and }r_{2}<0\right)\text{ or }\left(r_{2}>0\text{ and }r_{1}<0\right)\text{ or }\left(r_{2}=0\text{ and }r_{1}\neq 0\right)\text{ or }\left(r_{1}=0\text{ and }r_{2}\neq 0\right)\\\frac{r_{2}-r_{1}}{r_{1}r_{2}},&\left(r_{1}>0\text{ and }r_{1}<r_{2}\right)\text{ or }\left(r_{2}<0\text{ and }r_{1}<r_{2}\right)\text{ or }r_{2}=r_{1}\\-\frac{r_{2}-r_{1}}{r_{1}r_{2}},&\left(r_{2}>0\text{ or }r_{1}<0\right)\text{ and }r_{2}<r_{1}\end{matrix}\right.$$

Differentiate w.r.t. r_1

$$\text{Indeterminate}$$