Arccos(-45)

In the real numbers, arccos(-45) is not defined (the domain of arccos is [-1, 1]).

If you allow complex values, the principal value is:

• arccos(-45) = π + i arccosh(45) = π + i ln(45 + sqrt(2024))
• Numerically ≈ 3.14159 + 4.49969 i

(There are other complex branches as well; this is the usual principal value.)