Let X be a non-empty set. Show that the only dense subset of X with respect...
Prove: Let A be a dense subset of (X, T), and let B be a non-empty open subset of X. Then An B Prove: Let A be a dense subset of (X, T), and let B be a non-empty open subset of X. Then An B
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...
show that the product metric space X and Y are topologically equivalent 2. Suppose that metric space (X, d) is topologically equivalent to (Y, dh) for i-, n. Show that the product metric spaces X = Π-x, and Y = Π, Y, are topologica equivalent. 2. Suppose that metric space (X, d) is topologically equivalent to (Y, dh) for i-, n. Show that the product metric spaces X = Π-x, and Y = Π, Y, are topologica equivalent.
9. Let X and Y be metric spaces, and let D be a dense subset of X. (For the definition of "dense, see Problem 4 at the end of Section 3.5.) (a) Let f : X → Y and g : X → Y be continuous functions. Suppose that f(d)gld) for all d E D. Prove that f and g are the same function.
A subset D of a metric space (X, d) is dense if every member of X is a limit of a sequence of elements from D. Suppose (X,d) and (Y,ρ) are metric spaces and D is a dense subset of X. 1. Prove that if f : D -» Y is uniformly continuous then there exists an extension15 of f to a if dn (E D) e X define 7(x) lim f(d,) uniformly continuous function f:X * Y. Hint: 2....
Exercise 6.22 Given a non-empty subset A of a metric space X, prove that a pointe X is in a A iff da, A) = 0 = día, X\A), where daz, A) is defined as in Exercise 6.16.
Let S ⊂ R be a non-empty set. For any functions f and g from S into R, define d(f,g) := sup{|f(x)−g(x)| : x∈S}. Is d always a metric on the set F of functions from S into R? Why or why not? What does your answer suggest that we do to find a (useful) subset of functions from S to R on which d is a metric, if F does not work? Give a brief justification for your fix.
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...
5. Let S be a non empty bounded subset of R. If a > 0, show that sup (as) = a sup S where as = {as : ES}. Let c = sup S, show ac = sup (aS). This is done by showing (a) ac is an upper bound of aS. (b) If y is another upper bound of as then ac S7 Both are done using definitions and the fact that c=sup S.
5. Let S be a non-empty bounded subset of R. If a > 0, show that sup (aS) = a sup S where aS = {as : s E S}. Let c = sup S, show ac = sup (aS). This is done by showing: (a) ac is an upper bound of aS. (b) If y is another upper bound of aS then ac < 7. Both are done using definitions and the fact that c=sup S.