code for diagram

> regon:=[[1,1],[0,0],seq([i/50,sqrt(i/50)],i=0..50)]:

> plotregon:=plots[polygonplot](regon,color=tan,style=patch):

> p5:=plot({sqrt(x),x},x=-.3..1.3,thickness=3):

> txt3:=plots[textplot]({[.7,1,`y=sqrt(x)`],[1.2,1,`y=x`]},
font=[TIMES,BOLD,16]):

> plots[display]({plotregon,p5,txt3},xtickmarks=[1],
ytickmarks=[1],font=[TIMES,BOLD,16]);