public void FindRoot_QuadraticIncorrectIntialGuess_ReturnsRootWithinTolerance()
{
OneDimensionalFunction f = x => x * x;
OneDimensionalFunction fPrime = x => 2 * x;
const double initialGuess = 4;
NewtonRhapsonSolver solver = new NewtonRhapsonSolver(f, fPrime, initialGuess);
var root = solver.FindRoot();
Assert.IsTrue(Math.Abs(f(root)) < solver.Tolerance);
}
public void FindRoot_CosFunction_ReturnsRootWithinTolerance()
{
OneDimensionalFunction f = Math.Cos;
OneDimensionalFunction fPrime = x => - Math.Sin(x);
const double initialGuess = .5;
NewtonRhapsonSolver solver = new NewtonRhapsonSolver(f, fPrime, initialGuess);
var root = solver.FindRoot();
Assert.IsTrue(Math.Abs(f(root)) < solver.Tolerance);
}
public void FindRoot_PolynomialExactIntialGuess_ReturnsExactRoot()
{
OneDimensionalFunction f = x => x * x - 4;
OneDimensionalFunction fPrime = x => 2 * x;
const double initialGuess = 2;
NewtonRhapsonSolver solver = new NewtonRhapsonSolver(f, fPrime, initialGuess);
var root = solver.FindRoot();
Assert.AreEqual(initialGuess, root);
}