Answer
$ \dfrac{1}{5} \sin (5x) +C $
Work Step by Step
Our aim is to solve the integral $ \int \cos (5x) \ dx$
Use formula:$ \int \cos (ax+b) \ dx =\dfrac{1}{a} \sin (ax+b)+C$
Let us consider that $a =5$ and $b=0$
Now, $ \int \cos (5x) \ dx=\dfrac{1}{5} \sin (5x) +C $
or, $= \dfrac{1}{5} \sin (5x) +C $
