Answer
$0.6$
Work Step by Step
We know that $\cos$ has a period of $2\pi$, hence $\cos(\theta)=\sin(\theta+2k\pi)$ where $k$ is an integer.
Therefore,
$\cos(\theta)+\cos(\theta+2\pi)+\cos(\theta+4\pi)\\
=\cos(\theta)+\cos(\theta)+\cos(\theta)\\
=0.2+0.2+0.2\\
=0.6$
