Exercise 5 (based on Tao). Let (X,d) be an arbitrary metric space. Prove the following statements (1) If a sequence is convergent in X, all its subsequences are converging to the same limit as the original sequence. (2) If a subsequence of a Cauchy sequence is convergent, then the whole sequence is convergent to the same limit as the subsequence. (3) Suppose that (X,d) is complete and Y S X is closed in (X,d). Then the space (Y,dlyxy) is complete....
B2. (a) Let I denote the interval 0,1 and let C denote the space of continuous functions I-R. Define dsup(f,g)-sup |f(t)-g(t) and di(f.g)f (t)- g(t)ldt (f,g E C) tEI (i) Prove that dsup is a metric on C (ii) Prove that di is a metric on C. (You may use any standard properties of continuous functions and integrals, provided you make your reasoning clear.) 6 i) Let 1 denote the constant function on I with value 1. Give an explicit...
Carefully and rigorously prove the following. Let X be a metric space. Show X is compact if and only if every sequence contains a convergent subse- quence. Hint for (): Argue by contradiction. If there was a sequence with no convergent subsequence, use that sequence to construct an open cover of X, such that every set in the cover contains only a finite number of elements of the sequence. Then use compactness to get a contradiction. Hint for (): Let...
Problem 2: For any x, y e R let d(x,y):-arctan(y) - arctan(x). Do the following: (1) Prove that d is a metric on R. (2) Letting xnn, prove that {xnJnE is a Cauchy sequence with no limit in R (Note that {xn)nen is NOT Cauchy under the Euclidean metric and that all Cauchy sequences in the Euclidean metric have a limit in R.) Problem 2: For any x, y e R let d(x,y):-arctan(y) - arctan(x). Do the following: (1) Prove...
и с е wіlucute a cИronic InTra myr и те т 2. If you forgot to read the ESR results at the 60 minutes mark and discovered your mistake at 95 minutes mark, what action do you take and how do you report the results?
(3 points.) Prove that the following properties hold in any vector space: (1) (-с)и %— — (си). (i) —(-и) %— (iii) (0)(x)= 0 и.
Problem 1. Let (X, d) be a metric space and t the metric topology on X. (a) Fix a E X. Prove that the map f :(X, T) + R defined by f(x) = d(a, x) is continuous. (b) If {x'n} and {yn} are Cauchy sequences, prove that {d(In, Yn)} is a Cauchy sequence in R.
3. Suppose X is a metric space with a sequence of points Xn e X with the property that for each n + m we have d(Xn, Xm) = 1. Prove that no subsequence of xn converges, and that therefore X is not compact. Hint: You could use the previous problem.
#9. all one problem. then e is 0U tric space. Show that there is an isometric imbedding h of X 、D), as follows: Let X denote the set of all space () into a complete metric Cauchy sequences of points of X. Define x~ y if Let [x] denote the equivalence class of x; and let Y denote the set of these eq x (xi, x2, ...) uiv alence classes. Define a metric D on Y by the equation linnod(xn,...
Q3 Preliminary material The homework assignment is found on the next page. Our goal in this homework is to develop an algorithm for solving equations of the form f (x) (1) = X where f is a function S S, for some S C R". This kind of problem is sometimes called fixed point problem, and a solution x of problem (1) is called a fixed point of f. The algorithm we will consider is the following: a Step 0....