Function tangent

code/geometry/circles.cpp:18–24

  r1 = H + v, r2 = H - v;
  return 1 + (abs(v) > EPS); }
int tangent(P(A), C(O, r), point &r1, point &r2) {
  point v = O - A; double d = abs(v);
  if (d < r - EPS) return 0;
  double alpha = asin(r / d), L = sqrt(d*d - r*r);
  v = normalize(v, L);
  r1 = A + rotate(v, alpha), r2 = A + rotate(v, -alpha);
  return 1 + (abs(v) > EPS); }
void tangent_outer(C(A,rA), C(B,rB), PP(P), PP(Q)) {
  // if (rA - rB > EPS) { swap(rA, rB); swap(A, B); }
  double theta = asin((rB - rA)/abs(A - B));