-0.5, -0.5),
      p2 = point( 1, -0.5), 
      p3 = point(   0,  1.5);
  
// Define two circles, one by wedging 3 points, one directly.
  var C = ()=>p1^p2^p3,        // a function so it updates live.
      D = circle(1,-1,0.9);
  
// Define two lines, one directly, one by wedging two points and infinity.
  var X=line(0,1,0), Y=()=>p2^p3^ei;
      
// Create point pairs by intersecting a circle(s) and a line(s).
  var pp1=()=>X&C, pp2=()=>C&D, pp3=()=>Y&D;
      
// Distances and angles.
  var dp1  = ()=>(