=begin
  # sample-geometry03.rb

  #incenter
  puts "too heavy ... skip (#{$0})"
  exit
  require 'algebra'
  
  R = MPolynomial(Rational)
  x,y,a1,a2,b1,b2,c1,c2 = R.vars('xya1a2b1b2c1c2')
  Q = LocalizedRing(R)
  x0,y0,a10,a20,b10,b20,c10,c20 = R.vars.map{|v| Q[v]}
  V = Vector(R, 2)
  W = Vector(Q, 2)
  X, A, B, C = V[x,y], V[a1,a2], V[b1,b2], V[c1,c2]
  
  def bisector(p1, p2, p3)
    p1,p2,p3 = [p1,p2,p3].map{|v| v.convert_to(W)}
    k1 = (p1.inner_product(p2))**2/p2.norm2
    k2 = (p1.inner_product(p3))**2/p3.norm2
    (k1-k2).numerator
  end
  
  def line(p1, p2, p3)
    SquareMatrix.det([[1, *p1], [1, *p2], [1, *p3]])
  end
  
  l1 = bisector(X-A, B-A, C-A)
  p l1
  l2 = bisector(X-B, C-B, A-B)
  p l2
  l3 = bisector(X-C, A-C, B-C)
  p l3
  
  s = line(A, B, C)
  
  g = Groebner.basis [l1, l2, l3, s-1] #s-1 means non degeneracy
  
  g.each do |f|
    p f
  end
  
  #p g.size > 1
((<_|CONTENTS>))
=end