There is no trigonometric arc cosine function built in to HyperCard.
Therefore, if you want to find the arc cosine of a value use the method
shown here.
The following takes the arc cosine of the value in field x and puts it in
field Result:
put (atan (sqrt (1 - fld"x" * fld"x") / fld"x") * 180)/pi into fld "Result"
This article is adapted from the Claris Tech Info database.