acos

import std.math.operations : isClose;
import std.math.constants : PI;
import std.math.trigonometry : std_math_acos = acos;
assert(acos(complex(0.0)) == std_math_acos(0.0));
assert(isClose(acos(complex(0.5L)), PI / 3));

import std.math.operations : isClose;
import std.math.constants : PI;
assert(asin(complex(0.0)) == 0.0);
assert(isClose(asin(complex(0.5L)), PI / 6));

import std.math.operations : isClose;
import std.math.constants : PI;
assert(atan(complex(0.0)) == 0.0);
assert(isClose(atan(sqrt(complex(3.0L))), PI / 3));
assert(isClose(atan(sqrt(complex(3.0f))), float(PI) / 3));