--- /dev/null
+/* origin: OpenBSD /usr/src/lib/libm/src/s_casinh.c */
+/*
+ * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Complex inverse hyperbolic sine
+ *
+ *
+ * SYNOPSIS:
+ *
+ * double complex casinh();
+ * double complex z, w;
+ *
+ * w = casinh (z);
+ *
+ *
+ * DESCRIPTION:
+ *
+ * casinh z = -i casin iz .
+ *
+ * ACCURACY:
+ *
+ * Relative error:
+ * arithmetic domain # trials peak rms
+ * IEEE -10,+10 30000 1.8e-14 2.6e-15
+ *
+ */
+
+#include "libm.h"
+
+double complex casinh(double complex z)
+{
+ // FIXME: -I, reeval
+ return -1.0 * I * casin(z * I);
+}