circumscribed :=
proc(a, b)
   # draws a 2D triangle with vertices (0,0), (1,0), (a,b) in green 
   # draws the circumscribed circle in red
   local mx, my, # coordinates of circumscribed circle
         r, # radius of circumscribed circle
         trian, circ # the two plots
         ;
   mx := 0.5;
   my := evalf( (-a + a^2 + b^2)/(2*b) ); # determined by Maple
   r := evalf( sqrt(mx^2 + my^2) );
   trian := plot([0,0, 1,0, a,b, 0,0], style=LINE, color=green);
   circ := plot([mx + r*cos(t), my + r*sin(t), t=0..2*Pi], color=red);
   plot[multiple]({trian,circ});
end;