Erf[2] returns Erf[2] but Erf[2.0] 0.995322

Questions
1

Hi,

After some lengthy troubleshooting I managed to narrow down the issue to the title. I am running Mathematica 13.1 on Zorin OS 16.2. Anyone else seeing this?

Thanks,
GW

2

This is how Mathematica fundamentally works, if you input an exact quantity it will return an exact quantity. Since Erf[2] can not be simply written, it will leave it as is; the simplest way is Erf[2]. If you input a machine-precision number 2.0, it will return a machine precision number. This is therefore expected behaviour.

Compare to e.g. Sin[30 Degree] which gives (exactly) 1/2, but Sin[30.0 Degree] gives 0.5. Hope this is clear. You can force numerical evaluation by doing N[Erf[2]].