how to prove something is an eigenvalue code example
Example 1: finding eigen values and eigen vectors of a matrix in matlab
[V,D] = eig(A)
Example 2: eigenvalue of matrix c++ using Eigen
int main(){
Eigen::Matrix<double, 2, 2> A; // declare a real (double) 2x2 matrix
A << 0, 2, 1, 0; // defined the matrix A
Eigen::EigenSolver<Eigen::Matrix<double, 2,2> > s(A); // the instance s(A) includes the eigensystem
std::cout << A << std::endl;
std::cout << "eigenvalues:" << std::endl;
std::cout << s.eigenvalues()(0) << std::endl;
std::cout << "eigenvectors=" << std::endl;
std::cout << s.eigenvectors() << std::endl;
return(0);
}