Let X and Y be sets. Let us say that a subset S of the cartesian product X x Y is a rectangle if S = A × B for some A C X and BCY. 10. (a) Prove that every one-element subset of X x Y is a rectangle. (b) Prove that whenever X is a set with more than one element, the subset {(x, æ) : ¤ € X} S = of X x X is not a rectangle. (Here Y = X.) (c) Is the union of two rectangles in X x Y always a rectangle? Give either a proof that this is true or an example to show that it is false.
Let X and Y be sets. Let us say that a subset S of the cartesian product X x Y is a rectangle if S = A × B for some A C X and BCY. 10. (a) Prove that every one-element subset of X x Y is a rectangle. (b) Prove that whenever X is a set with more than one element, the subset {(x, æ) : ¤ € X} S = of X x X is not a rectangle. (Here Y = X.) (c) Is the union of two rectangles in X x Y always a rectangle? Give either a proof that this is true or an example to show that it is false.
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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
Transcribed Image Text:Let X and Y be sets. Let us say that a subset S of the cartesian product X x Y is a
rectangle if S = A × B for some A C X and BCY.
10.
(a) Prove that every one-element subset of X x Y is a rectangle.
(b) Prove that whenever X is a set with more than one element, the subset
{(x, æ) : ¤ € X}
S =
of X x X is not a rectangle. (Here Y = X.)
(c) Is the union of two rectangles in X x Y always a rectangle? Give either a proof that
this is true or an example to show that it is false.
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