Evaluate the following integral using trigonometric substitution.

${\displaystyle \underset{0}{\overset{\frac{5}{2}}{}}}\frac{dx}{\sqrt[\phantom{2}]{25-x^2}}$

${\displaystyle \underset{0}{\overset{\frac{5}{2}}{}}}\frac{dx}{\sqrt[\phantom{2}]{25-x^2}}=($Type an exact answer.$)$