[fricas-devel] limit of erf at infinity

[Slawomir Kolodynski]

limit(erf(2*x+b),x=%plusInfinity) works fine, returning 1 as it should.
Similarly, limit(erf(-2*x+b),x=%plusInfinity) works.
However limit(erf(a*x+b),x=%plusInfinity) returns "failed", perhaps because
FriCAS does not know if a is positive or negative.
I tried to declare a:PositiveInteger, but that leads to an error " a is
declared as being in PositiveInteger but has not been given a value".

Is there a way to tell FriCAS that for example a>0 so that the limit can be
computed?

Slawomir

[oldk1331]

Hi,

FriCAS can not use the declaration to do inference.

For this specific problem, I suggest to use "a^2":

(3) -> limit(erf(a^2*x+b),x=%plusInfinity)

(3) 1

limit(erf(2*x+b),x=%plusInfinity) works fine, returning 1 as it should. Similarly, limit(erf(-2*x+b),x=%plusInfinity) works.
However limit(erf(a*x+b),x=%plusInfinity) returns "failed", perhaps because FriCAS does not know if a is positive or negative.
I tried to declare a:PositiveInteger, but that leads to an error " a is declared as being in PositiveInteger but has not been given a value".
Is there a way to tell FriCAS that for example a>0 so that the limit can be computed?
Slawomir
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