code: @Pure
  	@Inline(value = "2.*Math.sin(($1)/2.)", imported = {Math.class})
  	public static double crd(double angle) {
  		return 2. * Math.sin(angle / 2.);
  	}
docs: Replies the chord of the specified angle.
  
  <p><code>crd(a) = 2 sin(a/2)</code>
  
  <p><img src="./doc-files/chord.png" alt="[Chord function]">
  
  @param angle the angle.
  @return the chord of the angle.