Sum of Two Squares: Intro to Number Theory

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Writing an integer as the sum of two squares is rooted in significant theorems, such as Fermat's theorem, which states that primes of the form 4k+1 can be uniquely represented as such. Lagrange's theorem further expands this by asserting that any positive integer can be expressed as the sum of four squares. While there are intriguing properties associated with the sum of squares function, practical applications are limited. The primary motivation for studying this topic in number theory is intellectual curiosity rather than utility. Engaging with these concepts can enhance understanding of mathematical structures and relationships.
matqkks
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Why bother writing a given integer as the sum of two squares? Does this have any practical application? Is there an introduction on a first year number theory course which would motivate students to study the conversion of a given integer to sums of two squares?
 
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There is a good deal of material. For instance the corollary to a theorem of Fermat :- "Any prime ##p## of the form ##4k+1## can be represented uniquely as the sum of 2 squares. Or (related) Lagrange's theorem:- "Any positive integer ##n## can be written as the sum of 4 squares, some of which may be 0".
Then there are also many interesting properties of ##r_2(n)## where ##r## is the sum of squares function.
I would recommend you research "representations of integers as sums of squares."
 
matqkks said:
Why bother writing a given integer as the sum of two squares? Does this have any practical application?

It most likely does not. There are applications of number theory, but overall you should take the class mainly because you find it interesting, not because of possible applications.
 
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