Use constant for two pi

Author: kgryte

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

@@ -74,10 +74,10 @@ v = haversin( -3.141592653589793/6.0 );
 
 ```javascript
 var linspace = require( '@stdlib/math/utils/linspace' );
-var PI = require( '@stdlib/constants/math/float64-pi' );
+var TWO_PI = require( '@stdlib/constants/math/float64-two-pi' );
 var haversin = require( '@stdlib/math/base/special/haversin' );
 
-var x = linspace( 0.0, 2.0*PI, 100 );
+var x = linspace( 0.0, TWO_PI, 100 );
 var i;
 
 for ( i = 0; i < x.length; i++ ) {

lib/node_modules/@stdlib/math/base/special/haversin/examples/index.js

@@ -19,10 +19,10 @@
 'use strict';
 
 var linspace = require( '@stdlib/math/utils/linspace' );
-var PI = require( '@stdlib/constants/math/float64-pi' );
+var TWO_PI = require( '@stdlib/constants/math/float64-two-pi' );
 var haversin = require( './../lib' );
 
-var x = linspace( 0.0, 2.0*PI, 100 );
+var x = linspace( 0.0, TWO_PI, 100 );
 var i;
 
 for ( i = 0; i < x.length; i++ ) {