Differentiable applications












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Let $varphi: mathbb{R}^{m}rightarrow mathbb{R}$ be an application defined by $varphi (x) =f(x).g(x)$, where $f,g: mathbb{R}^{m} rightarrow mathbb{R}$ are linear functional. Prove that $varphi'(x)$ exists.



I found that $varphi'(x)v=f(v)g(x)+f(x)g(v)$, where $x,v in mathbb{R}^{m}$.
When I went to prove the existence of the derivative by definition($varphi(z+h)=varphi (z) + varphi '(z)h + r(h)$), I found the limit



$lim_{hrightarrow 0} frac{fleft ( h right )gleft ( h right ))}{left | h right |}$



But I can not prove that this limit is zero










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    $begingroup$
    Welcome to MSE! Can you edit your post to provide context, e.g. what have you tried? Where are you stuck? You'll find that these sorts of questions are generally better-received here than those of the form "here is my problem, solve it for me."
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    – platty
    Dec 11 '18 at 22:56
















1












$begingroup$


Let $varphi: mathbb{R}^{m}rightarrow mathbb{R}$ be an application defined by $varphi (x) =f(x).g(x)$, where $f,g: mathbb{R}^{m} rightarrow mathbb{R}$ are linear functional. Prove that $varphi'(x)$ exists.



I found that $varphi'(x)v=f(v)g(x)+f(x)g(v)$, where $x,v in mathbb{R}^{m}$.
When I went to prove the existence of the derivative by definition($varphi(z+h)=varphi (z) + varphi '(z)h + r(h)$), I found the limit



$lim_{hrightarrow 0} frac{fleft ( h right )gleft ( h right ))}{left | h right |}$



But I can not prove that this limit is zero










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    Welcome to MSE! Can you edit your post to provide context, e.g. what have you tried? Where are you stuck? You'll find that these sorts of questions are generally better-received here than those of the form "here is my problem, solve it for me."
    $endgroup$
    – platty
    Dec 11 '18 at 22:56














1












1








1





$begingroup$


Let $varphi: mathbb{R}^{m}rightarrow mathbb{R}$ be an application defined by $varphi (x) =f(x).g(x)$, where $f,g: mathbb{R}^{m} rightarrow mathbb{R}$ are linear functional. Prove that $varphi'(x)$ exists.



I found that $varphi'(x)v=f(v)g(x)+f(x)g(v)$, where $x,v in mathbb{R}^{m}$.
When I went to prove the existence of the derivative by definition($varphi(z+h)=varphi (z) + varphi '(z)h + r(h)$), I found the limit



$lim_{hrightarrow 0} frac{fleft ( h right )gleft ( h right ))}{left | h right |}$



But I can not prove that this limit is zero










share|cite|improve this question











$endgroup$




Let $varphi: mathbb{R}^{m}rightarrow mathbb{R}$ be an application defined by $varphi (x) =f(x).g(x)$, where $f,g: mathbb{R}^{m} rightarrow mathbb{R}$ are linear functional. Prove that $varphi'(x)$ exists.



I found that $varphi'(x)v=f(v)g(x)+f(x)g(v)$, where $x,v in mathbb{R}^{m}$.
When I went to prove the existence of the derivative by definition($varphi(z+h)=varphi (z) + varphi '(z)h + r(h)$), I found the limit



$lim_{hrightarrow 0} frac{fleft ( h right )gleft ( h right ))}{left | h right |}$



But I can not prove that this limit is zero







analysis






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 11 '18 at 23:09







Paula Carvalho

















asked Dec 11 '18 at 22:51









Paula CarvalhoPaula Carvalho

112




112








  • 1




    $begingroup$
    Welcome to MSE! Can you edit your post to provide context, e.g. what have you tried? Where are you stuck? You'll find that these sorts of questions are generally better-received here than those of the form "here is my problem, solve it for me."
    $endgroup$
    – platty
    Dec 11 '18 at 22:56














  • 1




    $begingroup$
    Welcome to MSE! Can you edit your post to provide context, e.g. what have you tried? Where are you stuck? You'll find that these sorts of questions are generally better-received here than those of the form "here is my problem, solve it for me."
    $endgroup$
    – platty
    Dec 11 '18 at 22:56








1




1




$begingroup$
Welcome to MSE! Can you edit your post to provide context, e.g. what have you tried? Where are you stuck? You'll find that these sorts of questions are generally better-received here than those of the form "here is my problem, solve it for me."
$endgroup$
– platty
Dec 11 '18 at 22:56




$begingroup$
Welcome to MSE! Can you edit your post to provide context, e.g. what have you tried? Where are you stuck? You'll find that these sorts of questions are generally better-received here than those of the form "here is my problem, solve it for me."
$endgroup$
– platty
Dec 11 '18 at 22:56










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