Showing that a multivariable function is Borel measurable. [closed]












1












$begingroup$


I want to show that the following function is Borel measurable. Consider:
$$f: mathbb{R}^2 rightarrow mathbb{R}:left{
begin{array}{ll}
sinleft(frac{1}{x-y}right) & x> y \
x^2 + y^2 & xleq y. \
end{array}
right. $$



So I think one can prove it by looking if the function is continuous (so measurable) or proving it by the defintition of a Borel measurable function. By proving it from the defenition, one can use that ${x:f(x)>a}$ is a Borel set. But I don't know how to proceed with this defenition.










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$endgroup$



closed as off-topic by Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy Jan 6 at 20:54


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy

If this question can be reworded to fit the rules in the help center, please edit the question.





















    1












    $begingroup$


    I want to show that the following function is Borel measurable. Consider:
    $$f: mathbb{R}^2 rightarrow mathbb{R}:left{
    begin{array}{ll}
    sinleft(frac{1}{x-y}right) & x> y \
    x^2 + y^2 & xleq y. \
    end{array}
    right. $$



    So I think one can prove it by looking if the function is continuous (so measurable) or proving it by the defintition of a Borel measurable function. By proving it from the defenition, one can use that ${x:f(x)>a}$ is a Borel set. But I don't know how to proceed with this defenition.










    share|cite|improve this question









    $endgroup$



    closed as off-topic by Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy Jan 6 at 20:54


    This question appears to be off-topic. The users who voted to close gave this specific reason:


    • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy

    If this question can be reworded to fit the rules in the help center, please edit the question.



















      1












      1








      1





      $begingroup$


      I want to show that the following function is Borel measurable. Consider:
      $$f: mathbb{R}^2 rightarrow mathbb{R}:left{
      begin{array}{ll}
      sinleft(frac{1}{x-y}right) & x> y \
      x^2 + y^2 & xleq y. \
      end{array}
      right. $$



      So I think one can prove it by looking if the function is continuous (so measurable) or proving it by the defintition of a Borel measurable function. By proving it from the defenition, one can use that ${x:f(x)>a}$ is a Borel set. But I don't know how to proceed with this defenition.










      share|cite|improve this question









      $endgroup$




      I want to show that the following function is Borel measurable. Consider:
      $$f: mathbb{R}^2 rightarrow mathbb{R}:left{
      begin{array}{ll}
      sinleft(frac{1}{x-y}right) & x> y \
      x^2 + y^2 & xleq y. \
      end{array}
      right. $$



      So I think one can prove it by looking if the function is continuous (so measurable) or proving it by the defintition of a Borel measurable function. By proving it from the defenition, one can use that ${x:f(x)>a}$ is a Borel set. But I don't know how to proceed with this defenition.







      functional-analysis measure-theory borel-sets






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      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 5 at 19:05









      Belgium_PhysicsBelgium_Physics

      325110




      325110




      closed as off-topic by Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy Jan 6 at 20:54


      This question appears to be off-topic. The users who voted to close gave this specific reason:


      • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy

      If this question can be reworded to fit the rules in the help center, please edit the question.







      closed as off-topic by Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy Jan 6 at 20:54


      This question appears to be off-topic. The users who voted to close gave this specific reason:


      • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Nosrati, Paul Frost, Cesareo, José Carlos Santos, amWhy

      If this question can be reworded to fit the rules in the help center, please edit the question.






















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