Syntax: @ACOS(X)
X = a numeric value between -1 and 1.
@ACOS returns the arc cosine of angle X. The result is
the angle (in radians) whose cosine is X and ranges from
0 to . To convert the result from radians to degrees,
use the @DEGREES function.
Examples:
@ACOS(1) = 0
@ACOS(R3) = 1.670963748, where R3 = -0.1
@DEGREES(@ACOS(0)) = 90
@ACOS(-20) = Error - @ACOS, domain is -1 <= x <= 1