function vturn(radians, v) {
  if (!v) v = [0, 1];
  var x = v[0],
      y = v[1],
      cs = Math.cos(-radians),
      sn = Math.sin(-radians);
  return [x * cs - y * sn,
          x * sn + y * cs];
}
/**
 ** Returns vector rotated by "radians" radians
 */
Returns vector rotated by "radians" radians
Returns vector rotated by " radians " radians
function vturn(radians, v) {
  if (!v) v = [0, 1];
  var x = v[0],
      y = v[1],
      cs = Math.cos(-radians),
      sn = Math.sin(-radians);
  return [x * cs - y * sn,
          x * sn + y * cs];
}
function vturn ( radians , v ) { if ( ! v ) v = [ 0 , 1 ] ; var x = v [ 0 ] , y = v [ 1 ] , cs = Math . cos ( - radians ) , sn = Math . sin ( - radians ) ; return [ x * cs - y * sn , x * sn + y * cs ] ; }
Returns vector rotated by "radians" radians
Returns vector rotated by " radians " radians