Fundamental Properties of Supremum and Infimum, Including sup(A + B) = sup(A) + sup(B)

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Real Analysis Study Help for Baby Rudin, Part 1.4. After reviewing the definition of supremum and infimum, I do three things: 1) work through the proof of Theorem 1.11 in Walter Rudin's textbook (Baby Rudin), "Principles of Mathematical Analysis" (about showing ordered sets with the least upper bound property also have the greatest lower bound property), 2) solve exercise 5 from Chapter 1 in Baby Rudin (show that A is a nonempty set of real numbers which is bounded below, then -A is bounded above and sup(-A) = -inf(A), and 3) prove that the supremum is an additive set function on subsets of the real numbers that are bounded above: sup(A + B) = sup(A) + sup(B).

#realanalysis #supremum #supandinf

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⏱️TIMESTAMPS⏱️
(0:00) Introduction and Infinity is Really Big article.
(1:12) Definition of supremum and examples.
(3:19) Least upper bound property and greatest lower bound property.
(4:13) Every set with the LUB property has the GLB property (Theorem 1.11 in Baby Rudin).
(7:35) Bonus: Solve exercise 5 in Chapter 1 of Baby Rudin.
(11:36) sup(A + B) = sup(A) + sup(B) (the supremum is an additive set function on the set of all subsets of the real numbers which are bounded above).

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Thanks!!!That was amazing....I think I learned it 😍

mzarinchang
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Dear professor Kinney thank you for sharing Theoretical part of the Sup
Could you please tell us what is the generalized approximation Formula for a Sup Norm
Thanks forwards

alute
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Hi i just want to clarify something, if the inf is not in the set you mention it doesnt have a greatest lower bound property 3:54, but in the example is does have a GLB property? 5:22

thehardlife
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Sir, please provide more content on this book, its been 2 months since part 1.4 came on your blog. Thankyou

DeepakKumar-gnuy
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Sir can I get PDF or programing please give me, I want to learn using mathematica
I am great fan your videos ...

ramkishansharma
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The lecture is good, but your just reading it. I could read a book and get the same. Would be good if you broke down specific statements are gave a more thorough intuition. Thats why people come to these videos, because their mind doesnt process the books efficiently.

sandfordstebbings