docs(ellipse.cc): add links to math resources

1 files changed, 6 insertions, 0 deletions

diff --git a/ellipse/ellipse.cc b/ellipse/ellipse.cc
index 514b262..bd4f773 100644
--- a/ellipse/ellipse.cc
+++ b/ellipse/ellipse.cc
@@ -75,6 +75,9 @@ void ellipse::calculate() {
   // involved, but it was just too boring... and probably out of the scope of
   // this project anyway.
 
+  // The ellipse perimeter calculations are interpretations of Srinivasa
+  // Ramanujan's (1887-1920) work on ellipse perimeter approximations.
+
   // You probably shouldn't try this on an ill-equipped computer...
   //  {
   //    double limit = std::numeric_limits<double>::infinity();
@@ -95,6 +98,9 @@ void ellipse::calculate() {
   //    double infinite_sum = 0;
   //    double h = std::pow(this->major - this->minor, 2) /
   //               std::pow(this->major + this->minor, 2);
+  //    // An optimized binomial coefficient calculation without recursion:
+  //    //
+  //    https://www.geeksforgeeks.org/space-and-time-efficient-binomial-coefficient/
   //    std::function<double(double, double)> binomial_coefficient =
   //        [](double n, double k) -> double {
   //      double r = 1;