title: Why sin(0.2*x + pi) is aperiodic function?
body: <p>I know this might be too easy to be a question... but I can't get why sin(0.2*x + pi) is aperiodic?..</p>
  
  <p>I tried to plot this in matlab and that's what I got:</p>
  
  <p><img src="https://i.stack.imgur.com/cySJO.png" alt="Matlab sin wave"></p>
  
  <p>That should be periodic right? Instead in "Schaum's Outline of Digital Signal Processing" book it says it's aperiodic</p>
  
  <p><img src="https://i.stack.imgur.com/hc6H4.png" alt="Solution of Schaum&#39;s Outline book"></p>