From $cos(x-y)$ to $f(x+y)$?












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Is it possible to transform $cos(x-y)$ into a function $f=f(x+y)$ to have:
$$cos(x-y)=f(x+y)$$?










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    1












    $begingroup$


    Is it possible to transform $cos(x-y)$ into a function $f=f(x+y)$ to have:
    $$cos(x-y)=f(x+y)$$?










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      Is it possible to transform $cos(x-y)$ into a function $f=f(x+y)$ to have:
      $$cos(x-y)=f(x+y)$$?










      share|cite|improve this question









      $endgroup$




      Is it possible to transform $cos(x-y)$ into a function $f=f(x+y)$ to have:
      $$cos(x-y)=f(x+y)$$?







      real-analysis complex-analysis trigonometry change-of-variable






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      asked Dec 5 '18 at 16:10









      Alessio BocciAlessio Bocci

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      567






















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          $begingroup$

          If it is true for $x=y$ you have that



          $1=f(2x)$ so



          $f(t)=f(2(frac{t}{2}))=1$



          But it is not possibile because $f=1$ not verify the condition $cos(x-y)=f(x-y)$.



          So there is not a function that verify your condition






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            $begingroup$

            No, because $cos(1-1)$ is different from $cos(2-0)$, so $f(2)$ can't be both of them at once.






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              2 Answers
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              2 Answers
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              1












              $begingroup$

              If it is true for $x=y$ you have that



              $1=f(2x)$ so



              $f(t)=f(2(frac{t}{2}))=1$



              But it is not possibile because $f=1$ not verify the condition $cos(x-y)=f(x-y)$.



              So there is not a function that verify your condition






              share|cite|improve this answer









              $endgroup$


















                1












                $begingroup$

                If it is true for $x=y$ you have that



                $1=f(2x)$ so



                $f(t)=f(2(frac{t}{2}))=1$



                But it is not possibile because $f=1$ not verify the condition $cos(x-y)=f(x-y)$.



                So there is not a function that verify your condition






                share|cite|improve this answer









                $endgroup$
















                  1












                  1








                  1





                  $begingroup$

                  If it is true for $x=y$ you have that



                  $1=f(2x)$ so



                  $f(t)=f(2(frac{t}{2}))=1$



                  But it is not possibile because $f=1$ not verify the condition $cos(x-y)=f(x-y)$.



                  So there is not a function that verify your condition






                  share|cite|improve this answer









                  $endgroup$



                  If it is true for $x=y$ you have that



                  $1=f(2x)$ so



                  $f(t)=f(2(frac{t}{2}))=1$



                  But it is not possibile because $f=1$ not verify the condition $cos(x-y)=f(x-y)$.



                  So there is not a function that verify your condition







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Dec 5 '18 at 16:13









                  Federico FalluccaFederico Fallucca

                  1,90219




                  1,90219























                      5












                      $begingroup$

                      No, because $cos(1-1)$ is different from $cos(2-0)$, so $f(2)$ can't be both of them at once.






                      share|cite|improve this answer









                      $endgroup$


















                        5












                        $begingroup$

                        No, because $cos(1-1)$ is different from $cos(2-0)$, so $f(2)$ can't be both of them at once.






                        share|cite|improve this answer









                        $endgroup$
















                          5












                          5








                          5





                          $begingroup$

                          No, because $cos(1-1)$ is different from $cos(2-0)$, so $f(2)$ can't be both of them at once.






                          share|cite|improve this answer









                          $endgroup$



                          No, because $cos(1-1)$ is different from $cos(2-0)$, so $f(2)$ can't be both of them at once.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered Dec 5 '18 at 16:13









                          ArthurArthur

                          113k7115197




                          113k7115197






























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