When its argument is a constrained floating-point expression, this function creates a constrained floating-point expression (that is, an instance of IlcFloatExp or one of its subclasses) which is equal to the arc sine (in the range -Pi/2 to Pi/2) of its argument x expressed in radians. The effects of this function are reversible.

When its argument is an unconstrained numeric value (that is, a value of type IlcFloat), this function returns the arc sine of its argument.

If you want to manipulate constrained floating-point expressions in degrees, we strongly recommend that you call the trigonometric functions on variables expressed in radians and then convert the results to degrees (rather than declaring the constrained floating-point expressions in degrees and then converting them to radians to call the trigonometric functions).

The reason for that advice is that the method we recommend gives more accurate results in the context of the usual floating-point pitfalls.