적분 $\displaystyle \int _ {-2} ^ {3} {\frac{1} {x ^ {2} +36} dx}$ 의 값은?

• ①$\displaystyle \frac{\pi} {36}$
• ②$\displaystyle \frac{\pi} {24}$
• ③$\displaystyle \frac{\pi} {12}$
• ④$\displaystyle \frac{\pi} {6}$
• ⑤$\displaystyle \frac{\pi} {4}$