Lemma. The Lebesgue measure of a point (or more precisely, a singleton) is 0.Proof. See this problem. ∎Claim. The Lebesgue measure of a countable set of points is 0.Proof. Let A = {x1, x2...
...a,b]) ≤ b - a. Consider a countable collection {En} of sets in K with [a,b] ⊆ ∪n∈N En. Γ = {En} is...
... to show that m*[a,b]≧b-aBy definition of out measure,let { In } be collection of open cover of [a,b],we have to show that Σl( In )≧b...
...same holds for T-1. For all countable collections { In } of open intervals,∑ λ(T( In )) = |α|∑ λ( In )....
...suppose that {Ek} is a countable, decreasing sequence of sets in A (meaning E1 ⊇ E2 ⊇ ...) with υ(Ek) <...