This looks like a bug. Can you open an issue for it?

Aaron Meurer

On Mon, Oct 16, 2017 at 10:15 AM,  <[email protected]> wrote:
> The following code was run using sympy version 1.0, python version 3.4,
> Anaconda installation.
>
>
> import sympy as spy
> import sympy.abc as abc
>
>
> N, k = spy.symbols('N, k', positive = True)
> es = 1 - (1 - 1/(2*N))**k
> e = 2*N*es
> spy.pprint(e)
> c0 = spy.limit(e, N, spy.oo)
> spy.pprint(c0)
> c1 = spy.limit(N*(e-c0), N, spy.oo)
> spy.pprint(c1)
> c2 = spy.limit((e-c0-c1/N)*(N*N), N, spy.oo)
> spy.pprint(c2)
> c2x = spy.limit(e*N*N-c0*N*N-c1*N, N, spy.oo)
> spy.pprint(c2x)
>
>
> It prints
>
>
>
>     ⎛           k    ⎞
>     ⎜  ⎛     1 ⎞     ⎟
> 2⋅N⋅⎜- ⎜1 - ───⎟  + 1⎟
>     ⎝  ⎝    2⋅N⎠     ⎠
> k
>    2
>   k    k
> - ── + ─
>   4    4
> -∞
>  3    2
> k    k    k
> ── - ── + ──
> 24   8    12
>
>
> As you can see, the result for c2 is wrong, although it is able to calculate
> c2x correctly.
>
> Can someone please clarify what is going on?
>
> Thanks!
>
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