Another way is with PlotLegends -> "AllExpressions"
PlotLegends -> "AllExpressions"
In the documentation for PlotLegends, the section on Possible Issues makes no sense, at least in recent versions of Mathematica.
PlotLegends
Try PlotLegends -> {#}. The Automatic setting seems to produce no legend if there is only one equation being plotted. That behavior does not seem to be documented. I don't know if it's intentional or a bug.
PlotLegends -> {#}
Automatic
