text: #include <unsupported/Eigen/MatrixFunctions>
  #include <iostream>
  
  using namespace Eigen;
  
  int main()
  {
    const double pi = std::acos(-1.0);
  
    MatrixXd A(2,2);
    A << cos(pi/3), -sin(pi/3), 
         sin(pi/3),  cos(pi/3);
    std::cout << "The matrix A is:\n" << A << "\n\n";
    std::cout << "The matrix square root of A is:\n" << A.sqrt() << "\n\n";
    std::cout << "The square of the last matrix is:\n" << A.sqrt() * A.sqrt() << "\n";
  }
  