arccos
The trigonometric arccosine function.
Syntax

arccos(x)

x
is a real or complex number

Description
For real values, arccos is the inverse of the restriction of the trigonometric cosine function to [0, π]; the domain is [−1, 1].
In general, arccos(z)
is defined as
arccos(z) = π/2 + i⋅ln(i⋅z + √(1 − z^2))
where z
is a complex number. Notice that the general definition will be used also for real arguments outside of [−1, 1].
Examples
arccos(√3/2)
0.523598775598 (=π/6)
arccos(−1/2)
2.09439510239 (=(2/3)⋅π)
arccos(2)
1.31695789692⋅i
arccos(i)
1.57079632679 − 0.88137358702⋅i