I am trying to find a real number function or the equivalent in Excel.

I need to evaluate an arccos, but I can only use the real number answers. Here's the formula I'm working with:

Probability.pdf

And here's the Excel file:

Real Numbers.xls

The inputs for each calculation are in column A and the corresponding formulas are in column C. So far I'm only getting a #VALUE error except for one return.

I've checked several books without success and I've done several searches online, but real number is so vague a phrase, none of the search results have been what I'm looking for (mostly dealing with converting text in "real" (actual, not written out) numbers).

Ideally there would be a basic function for this so I would only have to type REAL(ACOS(X)), but that doesn't seem to be the case (or I just haven't found it).

Thanks for the help.