1 files changed, 44 insertions, 0 deletions
diff --git a/sysdeps/generic/asin.c b/sysdeps/generic/asin.c
new file mode 100644
index 0000000000..e75ee3d87e
--- /dev/null
+++ b/sysdeps/generic/asin.c
@@ -0,0 +1,44 @@
+/* Copyright (C) 1991 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <ansidecl.h>
+#include <errno.h>
+#include <math.h>
+
+/* Return the inverse sine of X.  */
+double
+DEFUN(asin, (x), double x)
+{
+  double abs_x;
+
+  if (__isnan(x))
+    {
+      errno = EDOM;
+      return x;
+    }
+
+  abs_x = fabs(x);
+
+  if (abs_x <= 0.5)
+    return atan2(x, sqrt(1.0 - (x * x)));
+  else
+    {
+      double t = 1.0 - abs_x;
+      return atan2(x, sqrt((t + t) - (t * t)));
+    }
+}