code: public static BigFloat cos(BigFloat x) {
  		if(x.isSpecial())
  			return NaN;
  		return x.context.valueOf(BigDecimalMath.cos(x.value, x.context.mathContext));
  	}
docs: Returns the {@link BigFloat} that is <code>cos(x)</code>.
  
  @param x the value
  
  @return the resulting {@link BigFloat}
  
  @see BigDecimalMath#cos(BigDecimal, MathContext)