(a) Prove that ANBCANB.Give an example to show that equality does not always hold.

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter7: Analytic Trigonometry
Section7.3: The Addition And Subtraction Formulas
Problem 80E
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How do you prove (a)?

Note that the bar represents the closure of a set

Def. 6 (Closure)
We say that x belongs to the closure of S, and we write x E S, if x is in the interior or the boundary, that is,
S = Sint U aS. This is the same as saying that
S = {x E R" : Ve > 0,
B(x; €, )NS+0}.
Transcribed Image Text:Def. 6 (Closure) We say that x belongs to the closure of S, and we write x E S, if x is in the interior or the boundary, that is, S = Sint U aS. This is the same as saying that S = {x E R" : Ve > 0, B(x; €, )NS+0}.
Let A and Bdenote subsets of R".
(a) Prove that ANBCAN B. Give an example to show that equality does not always hold.
(b) Prove that A° U B° C (AU B)°. Give an example to show that equality does not always hold.
(c) Give an example of a function that is C2 but not C³.
Transcribed Image Text:Let A and Bdenote subsets of R". (a) Prove that ANBCAN B. Give an example to show that equality does not always hold. (b) Prove that A° U B° C (AU B)°. Give an example to show that equality does not always hold. (c) Give an example of a function that is C2 but not C³.
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