1const std = @import("../../std.zig");
 2const testing = std.testing;
 3const math = std.math;
 4const cmath = math.complex;
 5const Complex = cmath.Complex;
 6
 7/// Returns the arc-cosine of z.
 8pub fn acos(z: anytype) Complex(@TypeOf(z.re, z.im)) {
 9    const T = @TypeOf(z.re, z.im);
10    const q = cmath.asin(z);
11    return Complex(T).init(@as(T, math.pi) / 2 - q.re, -q.im);
12}
13
14test acos {
15    const epsilon = math.floatEps(f32);
16    const a = Complex(f32).init(5, 3);
17    const c = acos(a);
18
19    try testing.expectApproxEqAbs(0.5469737, c.re, epsilon);
20    try testing.expectApproxEqAbs(-2.4529128, c.im, epsilon);
21}