Update documentation on trignometric functions.

pkg/analysis_server/test/mock_sdk.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library testing.mock_sdk;
 
 import 'package:analyzer/file_system/file_system.dart' as resource;
 import 'package:analyzer/file_system/memory_file_system.dart' as resource;
 import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 207 matching lines @@
   static const MockSdkLibrary LIB_MATH = const MockSdkLibrary(
       'dart:math',
       '/lib/math/math.dart',
       '''
 library dart.math;
 const double E = 2.718281828459045;
 const double PI = 3.1415926535897932;
 const double LN10 =  2.302585092994046;
 T min<T extends num>(T a, T b) => null;
 T max<T extends num>(T a, T b) => null;
-external double cos(num x);
+external double cos(num radians);
 external num pow(num x, num exponent);
-external double sin(num x);
+external double sin(num radians);
 external double sqrt(num x);
 class Random {
   bool nextBool() => true;
   double nextDouble() => 2.0;
   int nextInt() => 1;
 }
 ''');
 
   static const MockSdkLibrary LIB_HTML = const MockSdkLibrary(
       'dart:html',
@@ skipping 207 matching lines @@
   bool get isInternal => shortName.startsWith('dart:_');
 
   @override
   bool get isShared => throw unimplemented;
 
   @override
   bool get isVmLibrary => throw unimplemented;
 
   UnimplementedError get unimplemented => new UnimplementedError();
 }