code: public static BigDecimal atan2(BigDecimal y, BigDecimal x) {
          return BigDecimalMath.atan2(y, x, defaultMathContext);
      }
docs: Calculates the arc tangens (inverted tangens) of {@link BigDecimal} y / x in the range -<i>pi</i> to <i>pi</i> using the default {@link MathContext}.
  
  @param y the {@link BigDecimal}
  @param x the {@link BigDecimal}
  @return the calculated arc tangens {@link BigDecimal} with the precision specified in the default {@link MathContext}
  @see #setDefaultMathContext(MathContext)
  @see #atan2(BigDecimal, BigDecimal)