--- /dev/null
+#include "libm.h"
+
+// FIXME
+
+/* asin(z) = -i log(i z + sqrt(1 - z*z)) */
+
+double complex casin(double complex z)
+{
+ double complex w;
+ double x, y;
+
+ x = creal(z);
+ y = cimag(z);
+ w = cpack(1.0 - (x - y)*(x + y), -2.0*x*y);
+ return clog(cpack(-y, x) + csqrt(w));
+}