Counting Lattice Points












1












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Lattice points are of great importance. I encountered a problem as follows:- given a circle of radius 'r' as x²+y²=r² the number of lattice points can take values . The options were (0,72,69,140). I tried the problem using complex numbers but couldn't figure out a short and sweet method to tackle the problem so I need help ! Please help me!😊










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$endgroup$












  • $begingroup$
    Are you counting the lattice points inside the circle, or the the lattice points on the circle itself?
    $endgroup$
    – Dylan
    Feb 1 at 10:35
















1












$begingroup$


Lattice points are of great importance. I encountered a problem as follows:- given a circle of radius 'r' as x²+y²=r² the number of lattice points can take values . The options were (0,72,69,140). I tried the problem using complex numbers but couldn't figure out a short and sweet method to tackle the problem so I need help ! Please help me!😊










share|cite|improve this question











$endgroup$












  • $begingroup$
    Are you counting the lattice points inside the circle, or the the lattice points on the circle itself?
    $endgroup$
    – Dylan
    Feb 1 at 10:35














1












1








1





$begingroup$


Lattice points are of great importance. I encountered a problem as follows:- given a circle of radius 'r' as x²+y²=r² the number of lattice points can take values . The options were (0,72,69,140). I tried the problem using complex numbers but couldn't figure out a short and sweet method to tackle the problem so I need help ! Please help me!😊










share|cite|improve this question











$endgroup$




Lattice points are of great importance. I encountered a problem as follows:- given a circle of radius 'r' as x²+y²=r² the number of lattice points can take values . The options were (0,72,69,140). I tried the problem using complex numbers but couldn't figure out a short and sweet method to tackle the problem so I need help ! Please help me!😊







elementary-number-theory complex-numbers integer-lattices






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share|cite|improve this question













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edited Jan 31 at 20:18









Jyrki Lahtonen

110k13172390




110k13172390










asked Jan 31 at 19:02









Aditya GargAditya Garg

23413




23413












  • $begingroup$
    Are you counting the lattice points inside the circle, or the the lattice points on the circle itself?
    $endgroup$
    – Dylan
    Feb 1 at 10:35


















  • $begingroup$
    Are you counting the lattice points inside the circle, or the the lattice points on the circle itself?
    $endgroup$
    – Dylan
    Feb 1 at 10:35
















$begingroup$
Are you counting the lattice points inside the circle, or the the lattice points on the circle itself?
$endgroup$
– Dylan
Feb 1 at 10:35




$begingroup$
Are you counting the lattice points inside the circle, or the the lattice points on the circle itself?
$endgroup$
– Dylan
Feb 1 at 10:35










1 Answer
1






active

oldest

votes


















5












$begingroup$

Hint, if you believe that exactly one of the 4 given choices is correct: the center of the circle is a lattice point, and has a property all the other lattice points lack.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
    $endgroup$
    – Jyrki Lahtonen
    Jan 31 at 20:20










  • $begingroup$
    Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
    $endgroup$
    – Aditya Garg
    Jan 31 at 20:33












  • $begingroup$
    Do you mean use Gauss integers factorization ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:12










  • $begingroup$
    Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:17






  • 2




    $begingroup$
    Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
    $endgroup$
    – kimchi lover
    Jan 31 at 21:23












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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









5












$begingroup$

Hint, if you believe that exactly one of the 4 given choices is correct: the center of the circle is a lattice point, and has a property all the other lattice points lack.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
    $endgroup$
    – Jyrki Lahtonen
    Jan 31 at 20:20










  • $begingroup$
    Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
    $endgroup$
    – Aditya Garg
    Jan 31 at 20:33












  • $begingroup$
    Do you mean use Gauss integers factorization ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:12










  • $begingroup$
    Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:17






  • 2




    $begingroup$
    Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
    $endgroup$
    – kimchi lover
    Jan 31 at 21:23
















5












$begingroup$

Hint, if you believe that exactly one of the 4 given choices is correct: the center of the circle is a lattice point, and has a property all the other lattice points lack.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
    $endgroup$
    – Jyrki Lahtonen
    Jan 31 at 20:20










  • $begingroup$
    Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
    $endgroup$
    – Aditya Garg
    Jan 31 at 20:33












  • $begingroup$
    Do you mean use Gauss integers factorization ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:12










  • $begingroup$
    Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:17






  • 2




    $begingroup$
    Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
    $endgroup$
    – kimchi lover
    Jan 31 at 21:23














5












5








5





$begingroup$

Hint, if you believe that exactly one of the 4 given choices is correct: the center of the circle is a lattice point, and has a property all the other lattice points lack.






share|cite|improve this answer









$endgroup$



Hint, if you believe that exactly one of the 4 given choices is correct: the center of the circle is a lattice point, and has a property all the other lattice points lack.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Jan 31 at 20:00









kimchi loverkimchi lover

11.7k31229




11.7k31229












  • $begingroup$
    A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
    $endgroup$
    – Jyrki Lahtonen
    Jan 31 at 20:20










  • $begingroup$
    Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
    $endgroup$
    – Aditya Garg
    Jan 31 at 20:33












  • $begingroup$
    Do you mean use Gauss integers factorization ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:12










  • $begingroup$
    Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:17






  • 2




    $begingroup$
    Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
    $endgroup$
    – kimchi lover
    Jan 31 at 21:23


















  • $begingroup$
    A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
    $endgroup$
    – Jyrki Lahtonen
    Jan 31 at 20:20










  • $begingroup$
    Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
    $endgroup$
    – Aditya Garg
    Jan 31 at 20:33












  • $begingroup$
    Do you mean use Gauss integers factorization ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:12










  • $begingroup$
    Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
    $endgroup$
    – Jean Marie
    Jan 31 at 21:17






  • 2




    $begingroup$
    Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
    $endgroup$
    – kimchi lover
    Jan 31 at 21:23
















$begingroup$
A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
$endgroup$
– Jyrki Lahtonen
Jan 31 at 20:20




$begingroup$
A great hint. Even though we (ideally) stll need to perform a reality check given that there are two different sizes for the non-trivial orbits of $D_4$.
$endgroup$
– Jyrki Lahtonen
Jan 31 at 20:20












$begingroup$
Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
$endgroup$
– Aditya Garg
Jan 31 at 20:33






$begingroup$
Can I do something like n=(complex prime factorisation) and then use some combinatorics to end up at 4(pi(sigma{X(i^r)})) and thanks for the hint
$endgroup$
– Aditya Garg
Jan 31 at 20:33














$begingroup$
Do you mean use Gauss integers factorization ?
$endgroup$
– Jean Marie
Jan 31 at 21:12




$begingroup$
Do you mean use Gauss integers factorization ?
$endgroup$
– Jean Marie
Jan 31 at 21:12












$begingroup$
Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
$endgroup$
– Jean Marie
Jan 31 at 21:17




$begingroup$
Do we agree that your lattice is $mathbb{Z} times mathbb{Z}$ with center at the origin ?
$endgroup$
– Jean Marie
Jan 31 at 21:17




2




2




$begingroup$
Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
$endgroup$
– kimchi lover
Jan 31 at 21:23




$begingroup$
Yes. The number of lattice points inside the circle must be odd: the origin plus twice the number of pairs of non-zero lattice points $pmlambda$.
$endgroup$
– kimchi lover
Jan 31 at 21:23


















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