Math::Acos() Math::Acos(x): float Calculates arc cosine value of a number. Table 1. Parameters x number Real number x, with −1 ≤ x ≤ 1 Return The angle in radians whose cosine is x println(Math::Acos(-1)); // Will print "3.141593" println(Math::Acos(0.5)); // Will print "1.047198"