1 | initial version |

It is not clear what should the user enter, but if it is something like `sin(x)`

for `t`

and `pi`

for `u2`

, you have to understand that when you write `sin(x)`

in the command line, you create a symbolic object, corresponding to the mathematical function $sin(x)$. When you type "sin(x)" as an input of `raw_input()`

, the function returns the *string* "sin(x)", not the symbolic mathematical function. So you have to transform this string as a symbolic expression, that is an element of the symbolic ring, for this you should replace the string `t`

by `SR(t)`

(idem for `u2`

):

```
sage: SR(t).limit(x=SR(u2)+0.001)
```

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