anchor.diff:  }
   
   /**
  - * Returns the arc tangent of [a]/[b] with sign according to quadrant.
  + * A variant of [atan].
  + *
  + * Converts both arguments to doubles.
  + *
  + * Returns the angle between the positive x-axis and the vector ([b],[a]).
  + * The result, in radians, is in the range -PI..PI.
  + *
  + * If [b] is positive, this is the same as [:atan(b/a):].
  + *
  + * The result is negative when [a] is negative (including when [a] is the
  + * double -0.0).
  + *
  + * If [a] is equal to zero, the vector ([b],[a]) is considered parallel to
  + * the x-axis, even if [b] is also equal to zero. The sign of [b] determines
  + * the direction of the vector along the x-axis.
  + *
  + * Returns NaN if either argument is NaN.
    */
   external double atan2(num a, num b);
   
   /**
  - * If the [exponent] is an integer the result is of the same type as [x].
  - * Otherwise it is a [double].
  + * Returns [x] to the power of [exponent].
  + *
  + * If [x] is an [int] and [exponent] is a non-negative [int], the result is
  + * an [int], otherwise the result it is a [double].
  + *
  + * Notice that an [int] result cannot overflow, but a [double] result might
  + * be [double.INFINITY].
    */
   external num pow(num x, num exponent);
   
  -// TODO(4512): Add documentation.
  +/**
  + * Converts [x] to a double and returns the sine of the value.
  + *
  + * If [x] is not a finite number, the result is NaN.
  + */
   external double sin(num x);
  +
  +/**
  + * Converts [x] to a double and returns the cosine of the value.
  + *
  + * If [x] is not a finite number, the result is NaN.
  + */
   external double cos(num x);
  +
  +/**
  + * Converts [x] to a double and returns the tangent of the value.
  + *
  + * The tangent function is equivalent to [:sin(x)/cos(x):] and may be
  + * infinite (positive or negative) when [:cos(x):] is equal to zero.
  + * If [x] is not a finite number, the result is NaN.
  + */
   external double tan(num x);
  +
  +/**
  + * Converts [x] to a double and returns the arc cosine of the value.
  + *
  + * Returns a value in the range -PI..PI, or NaN if [x] is outside
  + * the range -1..1.
  + */
   external double acos(num x);
  +
  +/**
  + * Converts [x] to a double and returns the arc sine of the value.
  + * Returns a value in the range -PI..PI, or  NaN if [x] is outside
  + * the range -1..1.
  + */
   external double asin(num x);
  +
  +/**
  + * Converts [x] to a dobule and returns the arc tangent of the vlaue.
  + * Returns a value in the range -PI/2..PI/2, or NaN if [x] is NaN.
  + */
   external double atan(num x);
  +
  +/**
  + * Converts [x] to a double and returns the positive square root of the value.
  + *
  + * Returns -0.0 if [x] is -0.0, and NaN if [x] is otherwise negative or NaN.
  + */
   external double sqrt(num x);
  +
  +/**
  + * Converts [x] to a double and returns the natural exponent, [E],
  + * to the power [x].
  + * Returns NaN if [x] is NaN.
  + */
   external double exp(num x);
  +
  +/**
  + * Converts [x] to a double and returns the natural logarithm of the value.
  + * Returns negative infinity if [x] is equal to zero.
  + * Returns NaN if [x] is NaN or less than zero.
  + */
   external double log(num x);
  
positive.code: final double LN2 =  0.6931471805599453;
  
  /**
   * Base-2 logarithm of E.
   */
  final double LOG2E = 1.4426950408889634;
  
  /**
   * Base-10 logarithm of E.
   */
  final double LOG10E = 0.4342944819032518;
  
  
negative.code: 
  /**
   * Base of the natural logarithms.
   *
   * Typically written as "e".
   */
  final double E = 2.718281828459045;
  
  