Hi Emmanuel,
Thank you for your reply. Given the preliminary declarations
> *x = var("x")*
*h(x) = (x^2 + x + 2)/(x - 4)* ,
I've discovered that
*limit(**h**, x=4, dir="right")*
gives the confusing answer
*x |--> +Infinity* ,
but that by replacing *h* by *h(x)* one obtains the desired answer
*+Infinity* .
Put differently, the command I want should be written
*limit(**h(x)**, x=4, dir="right")* .
My confusion was caused in part by the S.D.S.U. SageMath Tutorial, but I
was also misled in part by two different styles for writing limits in the
mathematical literature.
Greg Grunberg
>
On Mon, May 13, 2019 at 4:47 AM Emmanuel Charpentier <
[email protected]> wrote:
> Let's see :
> sage: h(x)=(x^2+x+2)/(x-4)
> sage: h.parent()
> Callable function ring with argument x
> sage: limit(h,x=4,dir="right").parent()
> Callable function ring with argument x
> sage: h(x).parent()
> Symbolic Ring
> sage: limit(h(x),x=4,dir="right").parent()
> Symbolic Ring
> sage: limit(h(x),x=4,dir="right")
> +Infinity
>
> Is that clearer ?
>
> HTH,
>
>
> Le lundi 13 mai 2019 09:39:57 UTC+2, Greg1950 a écrit :
>>
>> I am using SageMath version 8.7, Release Date 2019-03-23, within a
>> Jupyter notebook. My operating system is Windows 10.
>>
>> I know some elementary Python programming, but am certainly not an
>> expert. I am essentially a newbie to SageMath.
>>
>> I defined, as per the S.D.S.U. Sage Tutorial, a function
>>
>> h(x) = (x^2 + x - 2)/(x - 4)
>>>
>>
>> Upon asking SageMath 8.7 to compute
>>
>> limit(h, x = 4, dir="right")
>>>
>>
>> I received as answer
>>
>> x |--> Infinity
>>>
>>
>> While the value of the (right-hand) limit is indeed Infinity, the " x
>> |--> " which precedes it in the "Out" cell suggests that the *argument* x
>> of the function h is approaching Infinity, while in fact it is the
>> *value* h(x) of the function which is doing so. The argument x itself
>> is approaching 4 from the right.
>>
>> So the *form* of the answer is misleading. It would be better if the
>> answer appeared simply as
>>
>> Infinity
>>>
>>
>> The answers to other limit calculations appear similarly to the above
>> example and may be similarly criticized.
>>
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