Inverse derivative












0














Note: $b(cdot)$ is a function, $G(cdot)$ is a cdf.



Given that $b(v) = beta$ and $b(v) = cfrac{1}{G(v)} int_{0}^{v}y_1 g(y_1)dy_1$ where $G(y_1) = Prob(Y_1 leq y_1) = F^{n-1}(y_1)$ where F is a CDF.



how do I find the derivative of the function:



$(v-beta)G(b^{-1}(beta))$ with respect to $beta$?



I know the rule is that if I have $y = f(x)$ then $x = f^{-1}(y)$ and



$$cfrac{df^{-1}(y)}{dy} = cfrac{1}{f'(x)}$$ but I am struggling to apply this my scenario.



the output should be:



$$-G(b^{-1}(beta)) + (v-b(b^{-1}(beta))g(b^{-1}(beta))cfrac{1}{b'(b^{-1}(beta))} =0$$



It is obvious for the first term, and by inspection I can even see that:



$b'(b^{-1}(beta)) = f'(x)$ in the above formula.



But as obvious as it may seem, I am having trouble seeing where exactly the $$(v-b(b^{-1}(beta))g(b^{-1}(beta))$$ is coming from, although I do note that $$G'(b^{-1}(beta)) = g(b^{-1}(beta))$$.



Any help in piecing this together is very much appreciated.










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  • Chain rule + derivative of the inverse function + $b(b^{-1}(beta))=beta$ ($b$ is monotone).
    – d.k.o.
    Nov 28 '18 at 5:33
















0














Note: $b(cdot)$ is a function, $G(cdot)$ is a cdf.



Given that $b(v) = beta$ and $b(v) = cfrac{1}{G(v)} int_{0}^{v}y_1 g(y_1)dy_1$ where $G(y_1) = Prob(Y_1 leq y_1) = F^{n-1}(y_1)$ where F is a CDF.



how do I find the derivative of the function:



$(v-beta)G(b^{-1}(beta))$ with respect to $beta$?



I know the rule is that if I have $y = f(x)$ then $x = f^{-1}(y)$ and



$$cfrac{df^{-1}(y)}{dy} = cfrac{1}{f'(x)}$$ but I am struggling to apply this my scenario.



the output should be:



$$-G(b^{-1}(beta)) + (v-b(b^{-1}(beta))g(b^{-1}(beta))cfrac{1}{b'(b^{-1}(beta))} =0$$



It is obvious for the first term, and by inspection I can even see that:



$b'(b^{-1}(beta)) = f'(x)$ in the above formula.



But as obvious as it may seem, I am having trouble seeing where exactly the $$(v-b(b^{-1}(beta))g(b^{-1}(beta))$$ is coming from, although I do note that $$G'(b^{-1}(beta)) = g(b^{-1}(beta))$$.



Any help in piecing this together is very much appreciated.










share|cite|improve this question






















  • Chain rule + derivative of the inverse function + $b(b^{-1}(beta))=beta$ ($b$ is monotone).
    – d.k.o.
    Nov 28 '18 at 5:33














0












0








0







Note: $b(cdot)$ is a function, $G(cdot)$ is a cdf.



Given that $b(v) = beta$ and $b(v) = cfrac{1}{G(v)} int_{0}^{v}y_1 g(y_1)dy_1$ where $G(y_1) = Prob(Y_1 leq y_1) = F^{n-1}(y_1)$ where F is a CDF.



how do I find the derivative of the function:



$(v-beta)G(b^{-1}(beta))$ with respect to $beta$?



I know the rule is that if I have $y = f(x)$ then $x = f^{-1}(y)$ and



$$cfrac{df^{-1}(y)}{dy} = cfrac{1}{f'(x)}$$ but I am struggling to apply this my scenario.



the output should be:



$$-G(b^{-1}(beta)) + (v-b(b^{-1}(beta))g(b^{-1}(beta))cfrac{1}{b'(b^{-1}(beta))} =0$$



It is obvious for the first term, and by inspection I can even see that:



$b'(b^{-1}(beta)) = f'(x)$ in the above formula.



But as obvious as it may seem, I am having trouble seeing where exactly the $$(v-b(b^{-1}(beta))g(b^{-1}(beta))$$ is coming from, although I do note that $$G'(b^{-1}(beta)) = g(b^{-1}(beta))$$.



Any help in piecing this together is very much appreciated.










share|cite|improve this question













Note: $b(cdot)$ is a function, $G(cdot)$ is a cdf.



Given that $b(v) = beta$ and $b(v) = cfrac{1}{G(v)} int_{0}^{v}y_1 g(y_1)dy_1$ where $G(y_1) = Prob(Y_1 leq y_1) = F^{n-1}(y_1)$ where F is a CDF.



how do I find the derivative of the function:



$(v-beta)G(b^{-1}(beta))$ with respect to $beta$?



I know the rule is that if I have $y = f(x)$ then $x = f^{-1}(y)$ and



$$cfrac{df^{-1}(y)}{dy} = cfrac{1}{f'(x)}$$ but I am struggling to apply this my scenario.



the output should be:



$$-G(b^{-1}(beta)) + (v-b(b^{-1}(beta))g(b^{-1}(beta))cfrac{1}{b'(b^{-1}(beta))} =0$$



It is obvious for the first term, and by inspection I can even see that:



$b'(b^{-1}(beta)) = f'(x)$ in the above formula.



But as obvious as it may seem, I am having trouble seeing where exactly the $$(v-b(b^{-1}(beta))g(b^{-1}(beta))$$ is coming from, although I do note that $$G'(b^{-1}(beta)) = g(b^{-1}(beta))$$.



Any help in piecing this together is very much appreciated.







calculus probability-distributions inverse-function






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asked Nov 28 '18 at 2:59









elbarto

1,538824




1,538824












  • Chain rule + derivative of the inverse function + $b(b^{-1}(beta))=beta$ ($b$ is monotone).
    – d.k.o.
    Nov 28 '18 at 5:33


















  • Chain rule + derivative of the inverse function + $b(b^{-1}(beta))=beta$ ($b$ is monotone).
    – d.k.o.
    Nov 28 '18 at 5:33
















Chain rule + derivative of the inverse function + $b(b^{-1}(beta))=beta$ ($b$ is monotone).
– d.k.o.
Nov 28 '18 at 5:33




Chain rule + derivative of the inverse function + $b(b^{-1}(beta))=beta$ ($b$ is monotone).
– d.k.o.
Nov 28 '18 at 5:33















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