Wrong answer for a simple limit

[videlec]

As reported in ask.sagemath.org we have

sage: f = exp(-x) / (2 + sin(x))
sage: f.limit(x=+infinity)
und

but it is clearly defined. And sympy gives the expected answer

sage: import sympy
sage: sympy.limit(f,x,+oo)
0

Upstream: Not yet reported upstream; Will do shortly.

CC: @kcrisman

Component: calculus

Keywords: bug, limit

Issue created by migration from https://trac.sagemath.org/ticket/17878

[videlec]

Description changed:

--- 
+++ 
@@ -1,7 +1,7 @@
 As reported in [ask.sagemath.org](http://ask.sagemath.org/question/25970/) we have
 
 ```
-sage: f = (e^(-x))/(2+ sin(x))
+sage: f = exp(-x) / (2 + sin(x))
 sage: f.limit(x=+infinity)
 und
 ```

[videlec]

Description changed:

--- 
+++ 
@@ -5,4 +5,10 @@
 sage: f.limit(x=+infinity)
 und
 ```
-but it is clearly defined!
+but it is clearly defined. And sympy gives the expected answer
+
+```
+sage: import sympy
+sage: sympy.limit(f,x,+oo)
+0
+```

[zimmermann6]

comment:4

here is another example of wrong limit (thanks Manuel Eberl, here with Sage 8.2):

sage: f=log(log(x + e^(log(x)*log(log(x)))))/log(log(log(x + e^x + log(x))))
sage: f.limit(x=+infinity)
0

The correct answer is 1. See https://sourceforge.net/p/maxima/bugs/3393/

[fchapoton]

Changed keywords from bug to bug, limit