Update readme

Author: Rinbo

lib/node_modules/@stdlib/math/base/special/cosc/README.md

@@ -18,4 +18,85 @@ limitations under the License.
 
 -->
 
-# Computes derivative of the cardinal sine function
+# cosc
+
+> Compute the derivative of the [cardinal sine][sinc] of a number.
+
+<section class="intro">
+
+The derivative of the normalized [cardinal sine][sinc] function is defined as
+
+` { cosc(x) = (cos( PI*x ) - sin( PI*x )/(PI*x)) / x } if x != 0, and 0 if x == 0 `
+
+
+<!-- </equation> -->
+
+for any real number `x`.
+
+</section>
+
+<!-- /.intro -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var cosc = require( '@stdlib/math/base/special/cosc' );
+```
+
+#### cosc( x )
+
+Computes the derivative of the normalized [cardinal sine][sinc] of a `number`.
+
+```javascript
+var v = cosc( 0.5 );
+
+// Return ~-1.273
+
+var x = cosc( -1.2 );
+
+// Return ~0.544
+
+var y = cosc( 0.0 );
+
+// Return 0
+
+var z = cosc( NaN );
+
+// Return NaN
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var linspace = require( '@stdlib/math/utils/linspace' );
+var cosc = require( '@stdlib/math/base/special/cosc' );
+
+var x = linspace( -5.0, 5.0, 100 );
+var i;
+
+for ( i = 0; i < x.length; i++ ) {
+    console.log( cosc( x[ i ] ) );
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+<section class="links">
+
+[sinc]: https://en.wikipedia.org/wiki/Sinc_function
+
+</section>
+
+<!-- /.links -->