title: Processing - rule of cosines (sss) - NaN
body: <p>I am working on a simple inverse kinematic delta robot controller with Processing. I am stuck at the rule of cosines. I have the length of the three sides and wish to get the angles. But <code>float angle = acos((sq(humerus)+sq(ulna) - sq(radius))/(2 * humerus * ulna));</code>
  always returns NaN. Any ideas?</p>