Plot complex functions

[GarkGarcia]

This is a follow up to mathics/Mathics#794:

When using Plot on a function with an imaginary part (e.g. Plot[Ix,{x,1,10}], only an empty coordinate system is returned. WolframAlpha's solution is to show two grafs: Plot[{Re[Ix],Re[Ix]},{x,1,10}]`, which might be a better default...

[mmatera]

This is true for Wolfram alpha, but not for WL, at least until v 11.3.0 :

Plot[Sin[x+2 I x],{x,-1,1}]

[GarkGarcia]

This is true for Wolfram alpha, but not for WL, at least until v 11.3.0 :

Plot[Sin[x+2 I x],{x,-1,1}]

Does that mean we're complying to "standard" bahaviour (the one exhibited by Mathematica)?