Merge branch '加入tan'

# Conflicts:
#	index.html

index.html

@@ -33,8 +33,7 @@
   function cos(a) {
     return Math.cos(a)
   }
-
-
+  
   function sin(a) {
     return Math.sin(a);
   }
@@ -46,6 +45,11 @@
   function acos(a) {
     return Math.acos(a);
   }
+
+  function tan(a) {
+    return Math.tan(a);
+  }
+
 </script>
 </body>
 </html>