1 files changed, 28 insertions, 0 deletions
diff --git a/lib/std/math/complex/asin.zig b/lib/std/math/complex/asin.zig
new file mode 100644
index 0000000000..76f94a286c
--- /dev/null
+++ b/lib/std/math/complex/asin.zig
@@ -0,0 +1,28 @@
+const std = @import("../../std.zig");
+const testing = std.testing;
+const math = std.math;
+const cmath = math.complex;
+const Complex = cmath.Complex;
+
+// Returns the arc-sine of z.
+pub fn asin(z: var) Complex(@typeOf(z.re)) {
+    const T = @typeOf(z.re);
+    const x = z.re;
+    const y = z.im;
+
+    const p = Complex(T).new(1.0 - (x - y) * (x + y), -2.0 * x * y);
+    const q = Complex(T).new(-y, x);
+    const r = cmath.log(q.add(cmath.sqrt(p)));
+
+    return Complex(T).new(r.im, -r.re);
+}
+
+const epsilon = 0.0001;
+
+test "complex.casin" {
+    const a = Complex(f32).new(5, 3);
+    const c = asin(a);
+
+    testing.expect(math.approxEq(f32, c.re, 1.023822, epsilon));
+    testing.expect(math.approxEq(f32, c.im, 2.452914, epsilon));
+}