Continuous - how can I combine these open sets

In summary: This can be extended to a product of compact spaces. Therefore, for ##f(x,y) \in C(X\times Y)##, there exists polynomials ##p_n(x,y)## that converge uniformly to ##f(x,y)##. This means that for any given ##\epsilon > 0##, there exists ##N\in \mathbb{N}## such that ##|f(x,y)-p_n(x,y)|<\epsilon## for all ##(x,y)\in X\times Y## and ##n>N##. Since each ##p_n(x,y)## is a polynomial, it can be written as a
  • #1
CornMuffin
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continuous -- how can I combine these open sets

Homework Statement


let ##X,Y## be compact spaces
if ##f \in C(X \times Y)## and ## \epsilon > 0##
then ## \exists g_1,\dots , g_n \in C(X) ## and ## h_1, \dots , h_n \in C(Y) ##
such that ##|f(x,y)- \Sigma _{k=1}^n g_k(x)h_k(y)| < \epsilon ## for all ##(x,y) \in X \times Y ##


Homework Equations






The Attempt at a Solution



##X,Y## are compact which means that for all open covers of ##X,Y##, there exists finite subcover.
So, i have been trying to think of a way to pick for all ## x_0 \in X ## and ## y_0 \in Y ##, a function ##g_{x_0} \in C(X)## and ## h_{y_0} \in C(Y) ## such that ##f(x_0,y_0) = g_{x_0}(x_0)h_{y_0}(y_0)## then there exists an open subset ##U_{x_0,y_0}## of ##X \times Y## such that ##|f(x,y) - g_{x_0}(x)h_{y_0}(y)| < \epsilon ## for all ##(x,y) \in U_{x_0,y_0} ##. Then we can form an open cover of ##X,Y## and so there is a finite subcover, ##U_1,\dots , U_n ##

but i don't know how I can combine these open sets to get my functions ##g_1,\dots ,g_n,h_1, \dots , h_n## such that ##|f(x,y)- \Sigma _{k=1}^n g_k(x)h_k(y)| < \epsilon ## for all ##(x,y) \in X \times Y ##
 
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Related to Continuous - how can I combine these open sets

What is the definition of continuous?

The definition of continuous is a function that has no sudden changes or breaks in its graph. This means that the function can be drawn without lifting the pen from the paper.

What are open sets?

Open sets are sets that do not contain their boundary points. In other words, for any point within the set, there exists a small neighborhood around that point that is also contained within the set.

How can I combine open sets?

To combine open sets, you can take the union or intersection of the two sets. The union contains all the elements that are in either set, while the intersection contains only the elements that are common to both sets.

Why is it important to be able to combine open sets?

Combining open sets allows us to create new sets that still maintain the properties of being open. This is important in many mathematical proofs and applications, as open sets play a crucial role in concepts such as continuity and convergence.

Can I combine an infinite number of open sets?

Yes, you can combine an infinite number of open sets using the same operations of union and intersection. However, the resulting set may not always be open, so it is important to carefully consider the sets being combined and their properties.

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