The acos() is an inbuilt function in Ruby which returns the inverse cosine of a number (argument) in radians. The value which is returned by the acos() function always lies between –pi to +pi.
Parameters: This function accepts one mandatory parameter value which specifies the value whose inverse cosine should be computed. It must lie between -1 and +1, else a domain-error is thrown.
Return Value: The function returns a numeric value between –pi and +pi. It is the counterclockwise angle which is measured in radian.
0.0 3.141592653589793 1.0471975511965979 2.3461938234056494
0.6435011087932843 2.8404561080364212 0.7377259684532488 1.9347802832764904