In[]:=
ℛ
1
={x^2+y^2==1&&x==y};
ℛ
2
={x==-y&&-1/2<x<1/2};​​rng1={{-a,a},{-a,a}}/.a->1;​​​​Show[​​Region[​​ImplicitRegion[
ℛ
1
,{x,y}],​​PlotRangerng1,Axes->True],​​Region[​​ImplicitRegion[
ℛ
2
,{x,y}],​​PlotRangerng1,Axes->True]]
Out[]=