diff --git a/base/special/ahavercos/README.md b/base/special/ahavercos/README.md
index dad4402e3..e1b2c233b 100644
--- a/base/special/ahavercos/README.md
+++ b/base/special/ahavercos/README.md
@@ -2,7 +2,7 @@
@license Apache-2.0
-Copyright (c) 2018 The Stdlib Authors.
+Copyright (c) 2024 The Stdlib Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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+## C APIs
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+### Usage
+
+```c
+#include "stdlib/math/base/special/ahavercos.h"
+```
+
+#### stdlib_base_ahavercos( x )
+
+Compute the [inverse half-value versed cosine][archavercosine] of a double-precision floating-point number (in radians).
+
+```c
+double out = stdlib_base_ahavercos( 0.0 );
+// returns ~3.1416
+```
+
+If `x < 0`, `x > 1`, or `x` is `NaN`, the function returns `NaN`.
+
+```c
+double out = stdlib_base_ahavercos( -3.14 );
+// returns NaN
+```
+
+The function accepts the following arguments:
+
+- **x**: `[in] double` input value.
+
+```c
+double stdlib_base_ahavercos( const double x );
+```
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+### Examples
+
+```c
+#include "stdlib/math/base/special/ahavercos.h"
+#include
+
+int main( void ) {
+ const double x[] = { -2.0, -1.6, -1.2, -0.8, -0.4, 0.4, 0.8, 1.2, 1.6, 2.0 };
+
+ double v;
+ int i;
+ for ( i = 0; i < 10; i++ ) {
+ v = stdlib_base_ahavercos( x[ i ] );
+ printf( "ahavercos(%lf) = %lf\n", x[ i ], v );
+ }
+}
+```
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