title: swift trigonometric functions (cos, tan, arcsin, arcos, arctan)
body: <p>hello I have to differenciate calculations in degrees and I have the following code but I doesn't return me the exact values. The only one right is the value of sin90 in degree = 1</p>
  
  <pre><code>//////***** DEGREES ******//////
  var sinus = sin(90.0 * M_PI / 180)
  var cosinus = cos(90 * M_PI / 180)
  var tangent = tan(90 * M_PI / 180)
  
  var arcsinus = asin(90 * M_PI / 180)
  var arcosinus = acos(90 * M_PI / 180)
  var arctangent = atan(90 * M_PI / 180)
  </code></pre>
  
  <p>What is the right operation to return the exact value for every operation in degree for cos, tan and their ARC functions? </p>