08. (3+2+1+1=7 marks) Let (E, d) be a metric space and let A be a non-empty...
(a) Suppose K is a compact subset of a metric space (X, d) and x є X but x K Show that there exist disjoint, open subsets of Gi and G2 of (X, d) such that r E Gi and KG2. (Hint: Use the version of compactness we called "having a compact topology." You will also need the Hausdorff property.) b) Now suppose that Ki and K2 are two compact, disjoint subsets of a metric space (X, d). Use (a)...
1. Let (X, d) be a metric space, and U, V, W CX subsets of X. (a) (i) Define what it means for U to be open. (ii) Define what it means for V to be closed. (iii) Define what it means for W to be compact. (b) Prove that in a metric space a compact subset is closed.
1.5.7 Prove the following separately Theorem 1.5.10. Let (X,d) be a metric space. (a) IfY is a compact subset of X, and Z C Y, then Z is compact if and only if Z is closed (b) IfY. Y are a finite collection of compact subsets of X, then their union Y1 U...UYn is also compact. (c) Every finite subset of X (including the empty set) is compact.
A. Let (X, d) be a metric space so that for every E X and every r>0 the closed ball N,(z) = {ye X : d(y, z) < r} is com pact. Let be a homeomorphism. (1) Prove that f"-+m-fn。fm for all n, m E Z. (2) Let z E X and suppose that F, {fn (z) : n E 2) is a closed subset of X Prove that F is a discrete subset of X (A subset Y C...
1. (a) Let d be a metric on a non-empty set X. Prove that each of the following are metrics on X: a a + i. d(1)(, y) = kd(x, y), where k >0; [3] ii. dr,y) d(2) (1, y) = [10] 1+ d(,y) The proof of the triangle inequality for d(2) boils down to showing b + > 1fc 1+a 1+b 1+c for all a, b, c > 0 with a +b > c. Proceed as follows to prove...
Let (X, d) be a metric space, and let ACX be a subset (a) (3 pts) Let x E X. Write the definition of d(x, A) (b) (7 pts) Assume A is closed. Prove that d(x,A-0 if and only if x E A. Let (X, d) be a metric space, and let ACX be a subset (a) (3 pts) Let x E X. Write the definition of d(x, A) (b) (7 pts) Assume A is closed. Prove that d(x,A-0 if...
(TOPOLOGY) Prove the following using the defintion: Exercise 56. Let (M, d) be a metric space and let k be a positive real number. We have shown that the function dk defined by dx(x, y) = kd(x,y) is a metric on M. Let Me denote M with metric d and let M denote M with metric dk. 1. Let f: Md+Mk be defined by f(x) = r. Show that f is continuous. 2. Let g: Mx + Md be defined...
REAL ANALYSIS Question 1 (1.1) Let A be a subset of R which is bounded above. Show that Sup A E A. (1.2) Let S be a subset of a metric space X. Prove that a subset T of S is closed in S if and only if T = SA K for some K which is closed in K. (1.3) Let A and B be two subsets of a metric space X. Recall that A°, the interior of A,...
1. Let (Q, d) be the metric space consisting of the set Q of rational numbers with the standard metric d(x, y) = (x – yl. Show that the Heine-Borel theorem fails for (Q, d). In other words, show that (Q, d) has a subset SCQ that is closed and bounded, but not compact (8 points).
Al. Let E be a non-empty set and let d:ExE0, oo). (a) Give the three conditions that d must satisfy to be a metric on E. (b) Ifa E E, r > 0 and 8 0, give the definition of the open ball BE(a) and the closed ball B (a) n-p) closure point of A. Hence, say what it means for A to be a closed subset of E 2 c) Say what it means for a sequence () in...