test: add missing test for math/base/special/cotd

PR-URL: #2449
Ref: c9ab1f2#commitcomment-143480610
Reviewed-by: Athan Reines <kgryte@gmail.com>

Author: gunjjoshi

lib/node_modules/@stdlib/math/base/special/cotd/test/test.js

@@ -108,3 +108,9 @@ tape( 'if provided `-infinity`, the function returns `NaN`', function test( t )
 	t.equal( isnan( v ), true, 'returns NaN' );
 	t.end();
 });
+
+tape( 'if provided `90.0`, the function returns `0.0`', function test( t ) {
+	var v = cotd( 90.0 );
+	t.equal( v, 0.0, 'returns expected value' );
+	t.end();
+});

lib/node_modules/@stdlib/math/base/special/cotd/test/test.native.js

@@ -117,3 +117,9 @@ tape( 'if provided `-infinity`, the function returns `NaN`', opts, function test
 	t.equal( isnan( v ), true, 'returns NaN' );
 	t.end();
 });
+
+tape( 'if provided `90.0`, the function returns `0.0`', opts, function test( t ) {
+	var v = cotd( 90.0 );
+	t.equal( v, 0.0, 'returns expected value' );
+	t.end();
+});