bigdec cos impl

public static BigDecimal cosine(BigDecimal x) {
		final int SCALE = 18;
		final int ROUNDING_MODE = BigDecimal.ROUND_HALF_EVEN;

		BigDecimal currentValue = BigDecimal.ONE;
		BigDecimal lastVal = currentValue.add(BigDecimal.ONE);
		BigDecimal xSquared = x.multiply(x);
		BigDecimal numerator = BigDecimal.ONE;
		BigDecimal denominator = BigDecimal.ONE;
		int i = 0;

		while(lastVal.compareTo(currentValue) != 0) {
			lastVal = currentValue;

			int z = 2 * i + 2;

			denominator = denominator.multiply(BigDecimal.valueOf(z));
			denominator = denominator.multiply(BigDecimal.valueOf(z - 1));
			numerator = numerator.multiply(xSquared);

			BigDecimal term = numerator.divide(denominator, SCALE + 5, ROUNDING_MODE);

			if(i % 2 != 0) {
				currentValue = currentValue.add(term);
			} else {
				currentValue = currentValue.subtract(term);
			}
			i++;
		}
		return currentValue;
	}