Pardon the geeky way for answering this, but this is the set of functions that are supported in the "Math" category of the expression parser. I think their behavior should be fairly self-explanatory.
You can use this, as in: Math.PI or Math.round(foo)
IRON_PARSER_VALUE(ParserMath, double, PI);
IRON_PARSER_METHOD_2(ParserMath, double, minimum, double, double);
IRON_PARSER_METHOD_2(ParserMath, double, maximum, double, double);
IRON_PARSER_METHOD_1(ParserMath, double, sqrt, double);
IRON_PARSER_METHOD_1(ParserMath, double, sin, double);
IRON_PARSER_METHOD_1(ParserMath, double, asin, double);
IRON_PARSER_METHOD_1(ParserMath, double, cos, double);
IRON_PARSER_METHOD_1(ParserMath, double, acos, double);
IRON_PARSER_METHOD_1(ParserMath, double, tan, double);
IRON_PARSER_METHOD_1(ParserMath, double, atan, double);
IRON_PARSER_METHOD_1(ParserMath, double, floor, double);
IRON_PARSER_METHOD_2(ParserMath, double, floorto, double, double);
IRON_PARSER_METHOD_1(ParserMath, double, ceil, double);
IRON_PARSER_METHOD_2(ParserMath, double, roundToSignificant, double, int);
IRON_PARSER_METHOD_1(ParserMath, double, normalizeAngleDegrees, double);
IRON_PARSER_METHOD_2(ParserMath, double, ceilto, double, double);
IRON_PARSER_METHOD_1(ParserMath, double, round, double);
IRON_PARSER_METHOD_2(ParserMath, double, roundto, double, double);
IRON_PARSER_METHOD_1(ParserMath, bool, isnan, double);
IRON_PARSER_METHOD_1(ParserMath, bool, abs, double);
Jeff