g ( r ) = ∫ 0 r x 2 + 4 d x d d x ∫ 0 r x 2 + 4 d x 1 c d o t r 2 + 4 d x − 0 2 + 4 d x {\displaystyle {\begin{aligned}g(r)=\int _{0}^{r}{\sqrt {x^{2}+4}}dx\\[2ex]{\frac {d}{dx}}\int _{0}^{r}{\sqrt {x^{2}+4}}dx\\[2ex]1cdot{\sqrt {r^{2}+4}}dx-{\sqrt {0^{2}+4}}dx\end{aligned}}}
![{\displaystyle {\begin{aligned}g(r)=\int _{0}^{r}{\sqrt {x^{2}+4}}dx\\[2ex]{\frac {d}{dx}}\int _{0}^{r}{\sqrt {x^{2}+4}}dx\\[2ex]1cdot{\sqrt {r^{2}+4}}dx-{\sqrt {0^{2}+4}}dx\end{aligned}}}](https://en.wikipedia.org/api/rest_v1/media/math/render/svg/14e18efeebac1ddaf1d1c8b74bd1b5c26eceaa2c)