anchor.diff:  
   /**
    * Mathematical constants and functions, plus a random number generator.
  - * 
  + *
    * To use this library in your code:
  - * 
  + *
    *     import 'dart:math';
    */
   library dart.math;
  
positive.code: external double asin(num x);
  
  /**
   * Converts [x] to a double and returns the arc tangent of the value.
   *
   * 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.
  
negative.code: external num pow(num x, num exponent);
  
  /**
   * Converts [radians] to a [double] and returns the sine of the value.
   *
   * If [radians] is not a finite number, the result is NaN.
   */
  external double sin(num radians);
  
  /**
   * Converts [radians] to a [double] and returns the cosine of the value.
   *
   * If [radians] is not a finite number, the result is NaN.
   */
  external double cos(num radians);
  
  /**
   * Converts [radians] to a [double] and returns the tangent of the value.
   *
   * The tangent function is equivalent to `sin(radians)/cos(radians)` and may be
   * infinite (positive or negative) when `cos(radians)` is equal to zero.
   * If [radians] is not a finite number, the result is NaN.
   */
  external double tan(num radians);
  
  /**
   * Converts [x] to a [double] and returns its arc cosine in radians.
   *
   * Returns a value in the range 0..PI, or NaN if [x] is outside
   * the range -1..1.
  