\item %% Section 2.4: Problems 8, 9, 10, 12, 14. % add 7 next time. %p85 Section 2.4: Problems 7(a), 8, 9, 10, 12, 13, 14. % add 7 next time. %p85 Remark: Problem 13 can be derived by way of quadratic approximation of $x=f^{-1}(y)$ at $(y,x) = (f(x_n), x_n)$ (as shown in the slides for the linear approximation). % \item % Use the code for Algorithm 2.2 to check if the standard fixed point iteration % $x_{n+1} = g(x_n) = 2 \cos(x_n)$ converge % to root of $f(x) = x-2\cos(x) = 0$. % If not, can you explain why? % Can you find a constant $\beta$ such that % the modified fixed point iteration % $x_{n+1} = \beta x_n + (1-\beta) g(x_n) $ converges % (at least locally)? \item % Section 2.5: Problems 12(a), 14, 15, 16. %p91 Section 2.5: Problems 12(a), 14, 16. %89 \item In Example 1 of section 2.5, the condition in Theorem 2.14 is not satisfied. Nevertheless, one could still get faster convergence of $\hat p_n$ than $p_n$, but of the same order. Analyze Aitken's $\Delta^2$ method to evaluate $\displaystyle{\lim_{n\to\infty}{\hat p_{n}-p \over p_{n+2} - p}}$. Then verify your result numerically. \end{enumerate} \end{document} % next time % \item % Another way of computing $\pi$ is given by the % Wallis formula % $$ % {\pi \over 2} = \prod_{n=1}^\infty \left( {(2n)^2 \over (2n-1)(2n+1) } \right). % $$ % There are two ways of computing the $N$-term approximation, % namely % $$ % {\pi_N \over 2}= % \left( {2\cdot 2 \over 1 \cdot 3} \right) % \left( {4\cdot 4 \over 3 \cdot 5} \right) % \left( {6\cdot 6 \over 5 \cdot 7} \right) \cdots %% \left( {2N\cdot 2N \over (2N-1) \cdot (2N+1)} \right) % \quad \mbox{or } % { 4^N (N!)^2 % \over % \left( \displaystyle{ \prod_{n=1}^N} (2n-1) \right) % \cdot \left( \displaystyle{ \prod_{n=1}^N} (2n+1) \right) % } % $$ % Which one is better in terms of the overflow issue? % What is the rate of convergence? % % Hint: The rate of convergence could be analyzed analytically % using Stirling's formula. This is not required in this problem, % but you can use that to help you check % your 'numerical rate of convergence'. % To find out the rate of convergence % numerically, it suffices to plot % $|\pi - \pi_N |$ as a function of $N$. % For example, % the two methods in problem 4 of section 1.3 give algebraic % rate $( N^{-k})$ and exponential rate $( q^{-N})$, respectively. % The difference can easily be observed by plotting the results. % The former appears as a straight line in the `loglog' plot % on matlab and the latter appears as a straight line in 'semilogy' plot. %