anchor.diff:    }
   }
   
  -/// The tangens function.
  +/// The tangens function. Expects input in `radians`.
   class Tan extends DefaultFunction {
     /// Creates a new tangens function with given argument expression.
     Tan(Expression arg) : super._unary('tan', arg);
  
positive.code:   String toString() => 'sqrt($arg)';
  }
  
  /// The sine function.
  class Sin extends DefaultFunction {
    /// Creates a new sine function with given argument expression.
    Sin(Expression arg) : super._unary('sin', arg);
  
negative.code:   }
  }
  
  /// The cosine function. Expects input in `radians`.
  class Cos extends DefaultFunction {
    /// Creates a new cosine function with given argument expression.
    Cos(Expression arg) : super._unary('cos', arg);
  