tan

import std.math.operations : isClose;
import std.math.traits : isIdentical;
import std.math.constants : PI;
import std.math.algebraic : sqrt;

assert(isIdentical(tan(0.0), 0.0));
assert(tan(PI).isClose(0, 0.0, 1e-10));
assert(tan(PI / 3).isClose(sqrt(3.0)));