code: public static BigDecimal reciprocal(BigDecimal x, MathContext mathContext) {
  		return BigDecimal.ONE.divide(x, mathContext);
  	}
docs: Calculates the reciprocal of the specified {@link BigDecimal}.
  
  @param x the {@link BigDecimal}
  @param mathContext the {@link MathContext} used for the result
  @return the reciprocal {@link BigDecimal}
  @throws ArithmeticException if x = 0
  @throws ArithmeticException if the result is inexact but the
  rounding mode is {@code UNNECESSARY} or
  {@code mc.precision == 0} and the quotient has a
  non-terminating decimal expansion.