Update documentation on trignometric functions.

runtime/lib/math_patch.dart

 // Copyright (c) 2012, 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.
 
 import "dart:typed_data";
 
 // A VM patch of the dart:math library.
 
 // If [x] is an [int] and [exponent] is a non-negative [int], the result is
 // an [int], otherwise the result is a [double].
@@ skipping 42 matching lines @@
     if (exponent != 0) {
       base *= base;
     }
   }
   return result;
 }
 
 @patch
 double atan2(num a, num b) => _atan2(a.toDouble(), b.toDouble());
 @patch
-double sin(num x) => _sin(x.toDouble());
+double sin(num radians) => _sin(radians.toDouble());
 @patch
-double cos(num x) => _cos(x.toDouble());
+double cos(num radians) => _cos(radians.toDouble());
 @patch
-double tan(num x) => _tan(x.toDouble());
+double tan(num radians) => _tan(radians.toDouble());
 @patch
 double acos(num x) => _acos(x.toDouble());
 @patch
 double asin(num x) => _asin(x.toDouble());
 @patch
 double atan(num x) => _atan(x.toDouble());
 @patch
 double sqrt(num x) => _sqrt(x.toDouble());
 @patch
 double exp(num x) => _exp(x.toDouble());
@@ skipping 137 matching lines @@
   }
 
   bool nextBool() {
     return _getBytes(1).isEven;
   }
 
   // Constants used by the algorithm.
   static const _POW2_32 = 1 << 32;
   static const _POW2_53_D = 1.0 * (1 << 53);
 }