Answer
$0.6$
Work Step by Step
As $\cos(\theta+2\pi)=\cos(\theta+4\pi)=\cos\theta$, we have
$\cos\theta+\cos(\theta+2\pi)+\cos(\theta+4\pi)=\cos{\theta}+\cos{\theta}+\cos{\theta}=3\cos\theta=3(0.2)=0.6$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.