Question about proof in a paper using fundamental theorem of calculus












1












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I'm reading a paper "Formal Guarantees on the Robustness of a Classifier against Adversarial Manipulation" https://arxiv.org/abs/1705.08475



There, I try to understand proof for Theorem 2.1. It starts with saying "By the main theorem of calculus, it holds that:"



$$
f_j(x+delta) = f_j(x) + int_0^1left<nabla f_j(x+tdelta),deltaright> d t, text{ for } j = 1,dots,K.
$$



Where, $f_j(x): mathbb{R}^d rightarrow mathbb{R}$, $delta in mathbb{R}^d$



A simple way to formulate the fundamental theorem of calculus would be:



$$
f_j(x+delta) = f_j(x) + left<nabla f_j(x+delta),deltaright> , text{ for } j = 1,dots,K.
$$



But I do not understand where the integral comes from, and why is it correct?










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$endgroup$

















    1












    $begingroup$


    I'm reading a paper "Formal Guarantees on the Robustness of a Classifier against Adversarial Manipulation" https://arxiv.org/abs/1705.08475



    There, I try to understand proof for Theorem 2.1. It starts with saying "By the main theorem of calculus, it holds that:"



    $$
    f_j(x+delta) = f_j(x) + int_0^1left<nabla f_j(x+tdelta),deltaright> d t, text{ for } j = 1,dots,K.
    $$



    Where, $f_j(x): mathbb{R}^d rightarrow mathbb{R}$, $delta in mathbb{R}^d$



    A simple way to formulate the fundamental theorem of calculus would be:



    $$
    f_j(x+delta) = f_j(x) + left<nabla f_j(x+delta),deltaright> , text{ for } j = 1,dots,K.
    $$



    But I do not understand where the integral comes from, and why is it correct?










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      I'm reading a paper "Formal Guarantees on the Robustness of a Classifier against Adversarial Manipulation" https://arxiv.org/abs/1705.08475



      There, I try to understand proof for Theorem 2.1. It starts with saying "By the main theorem of calculus, it holds that:"



      $$
      f_j(x+delta) = f_j(x) + int_0^1left<nabla f_j(x+tdelta),deltaright> d t, text{ for } j = 1,dots,K.
      $$



      Where, $f_j(x): mathbb{R}^d rightarrow mathbb{R}$, $delta in mathbb{R}^d$



      A simple way to formulate the fundamental theorem of calculus would be:



      $$
      f_j(x+delta) = f_j(x) + left<nabla f_j(x+delta),deltaright> , text{ for } j = 1,dots,K.
      $$



      But I do not understand where the integral comes from, and why is it correct?










      share|cite|improve this question









      $endgroup$




      I'm reading a paper "Formal Guarantees on the Robustness of a Classifier against Adversarial Manipulation" https://arxiv.org/abs/1705.08475



      There, I try to understand proof for Theorem 2.1. It starts with saying "By the main theorem of calculus, it holds that:"



      $$
      f_j(x+delta) = f_j(x) + int_0^1left<nabla f_j(x+tdelta),deltaright> d t, text{ for } j = 1,dots,K.
      $$



      Where, $f_j(x): mathbb{R}^d rightarrow mathbb{R}$, $delta in mathbb{R}^d$



      A simple way to formulate the fundamental theorem of calculus would be:



      $$
      f_j(x+delta) = f_j(x) + left<nabla f_j(x+delta),deltaright> , text{ for } j = 1,dots,K.
      $$



      But I do not understand where the integral comes from, and why is it correct?







      calculus proof-explanation






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 13 at 13:13









      mcsimmcsim

      1578




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