Answer
\begin{aligned}
\int \cos 2 x d x =\frac{1}{2} \sin 2 x+C
\end{aligned}
Work Step by Step
Given $$\int \cos 2 x d x $$
So, we have
\begin{aligned}
I&=\int \cos 2 x d x\\
&=\frac{1}{2} \int \cos 2 x \cdot 2 d x\\
&=\frac{1}{2} \sin 2 x+C
\end{aligned}
