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