title: calculate area and radius of circle using bash script
body: <pre><code>r=15
  phi=3.14
  d=30
  
  let area=$r*$r*phi
  echo $area
  
  let radius=2*$phi*$d
  echo $radius
  </code></pre>
  
  <p>when i run the code, show error "syntax error: invalid arithmetic operator (error token is ".14"). i haved searched on google relating this problem. the solution use bc (bash calculator). my question is is there other solution?</p>
  
  <p>second condition i change to 22/7 for phi. but the radius result not as expected
  the area calculation is correct 707 but the radius shoud be 188 not 180.</p>
  
  <p>thx</p>