From 4abab5ad6c8465a7528ccdd5f49367da05f78bbd Mon Sep 17 00:00:00 2001
From: Vladimir Azarov <avm@intermediate-node.net>
Date: Tue, 1 Oct 2024 15:47:05 +0200
Subject: Initial version

---
 src/complex/cacos.c | 11 +++++++++++
 1 file changed, 11 insertions(+)
 create mode 100644 src/complex/cacos.c

(limited to 'src/complex/cacos.c')

diff --git a/src/complex/cacos.c b/src/complex/cacos.c
new file mode 100644
index 0000000..c39d257
--- /dev/null
+++ b/src/complex/cacos.c
@@ -0,0 +1,11 @@
+#include "complex_impl.h"
+
+// FIXME: Hull et al. "Implementing the complex arcsine and arccosine functions using exception handling" 1997
+
+/* acos(z) = pi/2 - asin(z) */
+
+double complex cacos(double complex z)
+{
+	z = casin(z);
+	return CMPLX(M_PI_2 - creal(z), -cimag(z));
+}
-- 
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