code: function tan(angle) {
    utils.assertType(angle, 'unit', 'angle');
  
    var radians = angle.val;
  
    if (angle.type === 'deg') {
      radians *= Math.PI / 180;
    }
  
    var m = Math.pow(10, 9);
  
    var sin = Math.round(Math.sin(radians) * m) / m
      , cos = Math.round(Math.cos(radians) * m) / m
      , tan = Math.round(m * sin / cos ) / m;
  
    return new nodes.Unit(tan, '');
  }
docs: Return the tangent of the given `angle`.
  
  @param {Unit} angle
  @return {Unit}
  @api public