How to differentiate $ exp left{ int^t_sf(u)du right} $ w.r.t. $t$?












1












$begingroup$


I have looked and looked in my calculus books but couldn't find the answer to a problem I am facing of of the following form:



$$g(t) = exp left{ int^t_sf(u)du right} \
frac{partial g(t)}{partial t} = ? $$



How do I differentiate $g(t)$ w.r.t $t$?



$s$ is fixed.










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    1












    $begingroup$


    I have looked and looked in my calculus books but couldn't find the answer to a problem I am facing of of the following form:



    $$g(t) = exp left{ int^t_sf(u)du right} \
    frac{partial g(t)}{partial t} = ? $$



    How do I differentiate $g(t)$ w.r.t $t$?



    $s$ is fixed.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I have looked and looked in my calculus books but couldn't find the answer to a problem I am facing of of the following form:



      $$g(t) = exp left{ int^t_sf(u)du right} \
      frac{partial g(t)}{partial t} = ? $$



      How do I differentiate $g(t)$ w.r.t $t$?



      $s$ is fixed.










      share|cite|improve this question











      $endgroup$




      I have looked and looked in my calculus books but couldn't find the answer to a problem I am facing of of the following form:



      $$g(t) = exp left{ int^t_sf(u)du right} \
      frac{partial g(t)}{partial t} = ? $$



      How do I differentiate $g(t)$ w.r.t $t$?



      $s$ is fixed.







      calculus integration derivatives






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      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Jan 14 at 10:43









      BowPark

      560720




      560720










      asked Jan 13 at 21:15









      econmajorreconmajorr

      104




      104






















          3 Answers
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          $begingroup$

          It is a composite of the function $h(t):= exp(t)$ and $k(t):= int_s^t f(u) , mathrm{d} u$. By the chain rule we have $g'(t) = k'(t) h'(k(t))$. On the other hand, the fundamental theorem of calculus says that $k'(t) = f(t)$. Both together imply that
          $$g'(t) = k'(t) h'(k(t)) = f(t) exp(k(t)) = f(t) g(t).$$
          Note that this argument also proves that $g$ is differentiable. This steps are valid provided that $f$ is contiuous.






          share|cite|improve this answer











          $endgroup$





















            1












            $begingroup$

            Chain rule; we know how to differentiate $exp$ and we know how to differentiate $int_s^t f(u),du$ (the Fundamental Theorem), so we just combine those with the chain rule..






            share|cite|improve this answer









            $endgroup$





















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              $begingroup$

              We have $$frac{partial g(t)}{partial t}{=expleft{ int^t_sf(u)du right}cdot {partial int^t_sf(u)duover partial t}\=g(t)cdot Big(f(t)-f(s)Big)}$$can't proceed any further.






              share|cite|improve this answer









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                3 Answers
                3






                active

                oldest

                votes








                3 Answers
                3






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes









                1












                $begingroup$

                It is a composite of the function $h(t):= exp(t)$ and $k(t):= int_s^t f(u) , mathrm{d} u$. By the chain rule we have $g'(t) = k'(t) h'(k(t))$. On the other hand, the fundamental theorem of calculus says that $k'(t) = f(t)$. Both together imply that
                $$g'(t) = k'(t) h'(k(t)) = f(t) exp(k(t)) = f(t) g(t).$$
                Note that this argument also proves that $g$ is differentiable. This steps are valid provided that $f$ is contiuous.






                share|cite|improve this answer











                $endgroup$


















                  1












                  $begingroup$

                  It is a composite of the function $h(t):= exp(t)$ and $k(t):= int_s^t f(u) , mathrm{d} u$. By the chain rule we have $g'(t) = k'(t) h'(k(t))$. On the other hand, the fundamental theorem of calculus says that $k'(t) = f(t)$. Both together imply that
                  $$g'(t) = k'(t) h'(k(t)) = f(t) exp(k(t)) = f(t) g(t).$$
                  Note that this argument also proves that $g$ is differentiable. This steps are valid provided that $f$ is contiuous.






                  share|cite|improve this answer











                  $endgroup$
















                    1












                    1








                    1





                    $begingroup$

                    It is a composite of the function $h(t):= exp(t)$ and $k(t):= int_s^t f(u) , mathrm{d} u$. By the chain rule we have $g'(t) = k'(t) h'(k(t))$. On the other hand, the fundamental theorem of calculus says that $k'(t) = f(t)$. Both together imply that
                    $$g'(t) = k'(t) h'(k(t)) = f(t) exp(k(t)) = f(t) g(t).$$
                    Note that this argument also proves that $g$ is differentiable. This steps are valid provided that $f$ is contiuous.






                    share|cite|improve this answer











                    $endgroup$



                    It is a composite of the function $h(t):= exp(t)$ and $k(t):= int_s^t f(u) , mathrm{d} u$. By the chain rule we have $g'(t) = k'(t) h'(k(t))$. On the other hand, the fundamental theorem of calculus says that $k'(t) = f(t)$. Both together imply that
                    $$g'(t) = k'(t) h'(k(t)) = f(t) exp(k(t)) = f(t) g(t).$$
                    Note that this argument also proves that $g$ is differentiable. This steps are valid provided that $f$ is contiuous.







                    share|cite|improve this answer














                    share|cite|improve this answer



                    share|cite|improve this answer








                    edited Jan 14 at 10:10

























                    answered Jan 13 at 21:19









                    p4schp4sch

                    5,450318




                    5,450318























                        1












                        $begingroup$

                        Chain rule; we know how to differentiate $exp$ and we know how to differentiate $int_s^t f(u),du$ (the Fundamental Theorem), so we just combine those with the chain rule..






                        share|cite|improve this answer









                        $endgroup$


















                          1












                          $begingroup$

                          Chain rule; we know how to differentiate $exp$ and we know how to differentiate $int_s^t f(u),du$ (the Fundamental Theorem), so we just combine those with the chain rule..






                          share|cite|improve this answer









                          $endgroup$
















                            1












                            1








                            1





                            $begingroup$

                            Chain rule; we know how to differentiate $exp$ and we know how to differentiate $int_s^t f(u),du$ (the Fundamental Theorem), so we just combine those with the chain rule..






                            share|cite|improve this answer









                            $endgroup$



                            Chain rule; we know how to differentiate $exp$ and we know how to differentiate $int_s^t f(u),du$ (the Fundamental Theorem), so we just combine those with the chain rule..







                            share|cite|improve this answer












                            share|cite|improve this answer



                            share|cite|improve this answer










                            answered Jan 13 at 21:19









                            jmerryjmerry

                            15.3k1632




                            15.3k1632























                                0












                                $begingroup$

                                We have $$frac{partial g(t)}{partial t}{=expleft{ int^t_sf(u)du right}cdot {partial int^t_sf(u)duover partial t}\=g(t)cdot Big(f(t)-f(s)Big)}$$can't proceed any further.






                                share|cite|improve this answer









                                $endgroup$


















                                  0












                                  $begingroup$

                                  We have $$frac{partial g(t)}{partial t}{=expleft{ int^t_sf(u)du right}cdot {partial int^t_sf(u)duover partial t}\=g(t)cdot Big(f(t)-f(s)Big)}$$can't proceed any further.






                                  share|cite|improve this answer









                                  $endgroup$
















                                    0












                                    0








                                    0





                                    $begingroup$

                                    We have $$frac{partial g(t)}{partial t}{=expleft{ int^t_sf(u)du right}cdot {partial int^t_sf(u)duover partial t}\=g(t)cdot Big(f(t)-f(s)Big)}$$can't proceed any further.






                                    share|cite|improve this answer









                                    $endgroup$



                                    We have $$frac{partial g(t)}{partial t}{=expleft{ int^t_sf(u)du right}cdot {partial int^t_sf(u)duover partial t}\=g(t)cdot Big(f(t)-f(s)Big)}$$can't proceed any further.







                                    share|cite|improve this answer












                                    share|cite|improve this answer



                                    share|cite|improve this answer










                                    answered Jan 13 at 22:47









                                    Mostafa AyazMostafa Ayaz

                                    17k31039




                                    17k31039






























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