Manipulate[Plot[a*x*Sin[1/x],{x,0,100},PlotStyle->Blue,PlotRange->{{0,100},{0,5}},Epilog->{Text["\!\(\*UnderscriptBox[\(lim\), \(x -> \\ ∞\)]\)",{10,1.5}],Text[a x Sin[1/x],{20,1.5}],Text["(Overscript[=, 0  ∞])",{30,1.5}],Text[a,{35,1.5}]}],{a,1,5,1}]