In my previous post I figured out (thanks to D_Drmmr) how to calculate arc cosine with real numbers (including numbers not in the range -1;1).

Code:
_acos = -c*log(dotprods[j]+c*pow(one-pow(dotprods[j],2),0.5));
Anyway my application response times have increased by four times with this line

Is there any other way to calculate arc cosine (I am using VS2010 in a standard C++ project) faster?

Or is there any other possible engineering to make the program faster?


Thanks in advance