From 5e5c0ac2c3f80f14428c19293773245a8477aaaf Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sun, 13 Aug 2017 13:32:18 -0400
Subject: math: Add cotangent function.

* chickadee/math.scm (cotan): New procedure.
---
 chickadee/math.scm | 5 +++++
 doc/api.texi       | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/chickadee/math.scm b/chickadee/math.scm
index e9ebc6d..b695e92 100644
--- a/chickadee/math.scm
+++ b/chickadee/math.scm
@@ -18,6 +18,7 @@
 (define-module (chickadee math)
   #:export (pi
             pi/2
+            cotan
             square
             clamp
             min
@@ -28,6 +29,10 @@
 (define pi 3.14159265358979323846)
 (define pi/2 (/ pi 2.0))
 
+(define-inlinable (cotan z)
+  "Return the cotangent of Z."
+  (/ 1.0 (tan z)))
+
 (define-inlinable (square x)
   (* x x))
 
diff --git a/doc/api.texi b/doc/api.texi
index f5a2400..32a797b 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -429,6 +429,10 @@ approximation that is ``good enough.''
 Half of @var{pi}.
 @end defvar
 
+@deffn {Procedure} cotan @var{z}
+Return the cotangent of @var{z}.
+@end deffn
+
 @node Vectors
 @subsection Vectors
 
-- 
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