asin x
This calls Python's built-in math.asin function, which computes the arc sine of x.
math.asin
i1 : asin toPython 1 o1 = 1.5707963267948966 o1 : PythonObject of class float
i2 : asin toPython 0 o2 = 0.0 o2 : PythonObject of class float
The source of this document is in Python/doc/trig.m2:52:0.