Linearization using Taylor series












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$begingroup$


I'm trying to understand this approximation:



$x sqrt{bigg(1+alphaBig(frac{y}{x}-1Big)bigg)bigg/bigg(1+alphaBig(frac{x}{y}-1Big)bigg)} approx xbigg(1+frac{alpha}{2}Big(frac{y}{x}-1-frac{x}{y}+1Big)bigg)$



and this one:



$Largefrac{(x^3 (1-alpha)+y^3alpha)Big(frac{(1-alpha)}{x}+frac{alpha}{y}Big)}{(x(1-alpha)+yalpha)^2}approx 1+alphafrac{x}{y}bigg(frac{y^2}{x^2}-1bigg)^2$



According to the brief explanation, we derive the approximation using Taylor series linearization.



I'm familiar with Taylor expansion of $f(xpm ah)$, but not with linearization/approximation using Taylor.



I suspect there's some derivation involved, but I'm not too sure.



Can someone help?



enter image description here










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$endgroup$












  • $begingroup$
    If $f(x) = f(a) + f'(a)(x - a) + f''(a)/2! (x-a)^2 dots $ is the Taylor series of $f(x)$, then the linearization is just the first two terms: $L(x) = f(a) + f'(a)(x-a)$. Note that this is really just the tangent line to $f(x)$ at $x = a$.
    $endgroup$
    – JavaMan
    Dec 18 '18 at 20:20












  • $begingroup$
    I'm still confused, we have three variables, $x$ $y$ and $alpha$. How should I derivate the equation? With respect to $x$, $y$ or $alpha$?
    $endgroup$
    – JIM BOY
    Dec 18 '18 at 20:35










  • $begingroup$
    I believe $alpha$ is the variable that is infinitesimal. $x$ and $y$ can just be seen as some coefficients.
    $endgroup$
    – MoonKnight
    Dec 18 '18 at 21:15
















0












$begingroup$


I'm trying to understand this approximation:



$x sqrt{bigg(1+alphaBig(frac{y}{x}-1Big)bigg)bigg/bigg(1+alphaBig(frac{x}{y}-1Big)bigg)} approx xbigg(1+frac{alpha}{2}Big(frac{y}{x}-1-frac{x}{y}+1Big)bigg)$



and this one:



$Largefrac{(x^3 (1-alpha)+y^3alpha)Big(frac{(1-alpha)}{x}+frac{alpha}{y}Big)}{(x(1-alpha)+yalpha)^2}approx 1+alphafrac{x}{y}bigg(frac{y^2}{x^2}-1bigg)^2$



According to the brief explanation, we derive the approximation using Taylor series linearization.



I'm familiar with Taylor expansion of $f(xpm ah)$, but not with linearization/approximation using Taylor.



I suspect there's some derivation involved, but I'm not too sure.



Can someone help?



enter image description here










share|cite|improve this question









$endgroup$












  • $begingroup$
    If $f(x) = f(a) + f'(a)(x - a) + f''(a)/2! (x-a)^2 dots $ is the Taylor series of $f(x)$, then the linearization is just the first two terms: $L(x) = f(a) + f'(a)(x-a)$. Note that this is really just the tangent line to $f(x)$ at $x = a$.
    $endgroup$
    – JavaMan
    Dec 18 '18 at 20:20












  • $begingroup$
    I'm still confused, we have three variables, $x$ $y$ and $alpha$. How should I derivate the equation? With respect to $x$, $y$ or $alpha$?
    $endgroup$
    – JIM BOY
    Dec 18 '18 at 20:35










  • $begingroup$
    I believe $alpha$ is the variable that is infinitesimal. $x$ and $y$ can just be seen as some coefficients.
    $endgroup$
    – MoonKnight
    Dec 18 '18 at 21:15














0












0








0





$begingroup$


I'm trying to understand this approximation:



$x sqrt{bigg(1+alphaBig(frac{y}{x}-1Big)bigg)bigg/bigg(1+alphaBig(frac{x}{y}-1Big)bigg)} approx xbigg(1+frac{alpha}{2}Big(frac{y}{x}-1-frac{x}{y}+1Big)bigg)$



and this one:



$Largefrac{(x^3 (1-alpha)+y^3alpha)Big(frac{(1-alpha)}{x}+frac{alpha}{y}Big)}{(x(1-alpha)+yalpha)^2}approx 1+alphafrac{x}{y}bigg(frac{y^2}{x^2}-1bigg)^2$



According to the brief explanation, we derive the approximation using Taylor series linearization.



I'm familiar with Taylor expansion of $f(xpm ah)$, but not with linearization/approximation using Taylor.



I suspect there's some derivation involved, but I'm not too sure.



Can someone help?



enter image description here










share|cite|improve this question









$endgroup$




I'm trying to understand this approximation:



$x sqrt{bigg(1+alphaBig(frac{y}{x}-1Big)bigg)bigg/bigg(1+alphaBig(frac{x}{y}-1Big)bigg)} approx xbigg(1+frac{alpha}{2}Big(frac{y}{x}-1-frac{x}{y}+1Big)bigg)$



and this one:



$Largefrac{(x^3 (1-alpha)+y^3alpha)Big(frac{(1-alpha)}{x}+frac{alpha}{y}Big)}{(x(1-alpha)+yalpha)^2}approx 1+alphafrac{x}{y}bigg(frac{y^2}{x^2}-1bigg)^2$



According to the brief explanation, we derive the approximation using Taylor series linearization.



I'm familiar with Taylor expansion of $f(xpm ah)$, but not with linearization/approximation using Taylor.



I suspect there's some derivation involved, but I'm not too sure.



Can someone help?



enter image description here







taylor-expansion linearization






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asked Dec 18 '18 at 20:17









JIM BOYJIM BOY

356




356












  • $begingroup$
    If $f(x) = f(a) + f'(a)(x - a) + f''(a)/2! (x-a)^2 dots $ is the Taylor series of $f(x)$, then the linearization is just the first two terms: $L(x) = f(a) + f'(a)(x-a)$. Note that this is really just the tangent line to $f(x)$ at $x = a$.
    $endgroup$
    – JavaMan
    Dec 18 '18 at 20:20












  • $begingroup$
    I'm still confused, we have three variables, $x$ $y$ and $alpha$. How should I derivate the equation? With respect to $x$, $y$ or $alpha$?
    $endgroup$
    – JIM BOY
    Dec 18 '18 at 20:35










  • $begingroup$
    I believe $alpha$ is the variable that is infinitesimal. $x$ and $y$ can just be seen as some coefficients.
    $endgroup$
    – MoonKnight
    Dec 18 '18 at 21:15


















  • $begingroup$
    If $f(x) = f(a) + f'(a)(x - a) + f''(a)/2! (x-a)^2 dots $ is the Taylor series of $f(x)$, then the linearization is just the first two terms: $L(x) = f(a) + f'(a)(x-a)$. Note that this is really just the tangent line to $f(x)$ at $x = a$.
    $endgroup$
    – JavaMan
    Dec 18 '18 at 20:20












  • $begingroup$
    I'm still confused, we have three variables, $x$ $y$ and $alpha$. How should I derivate the equation? With respect to $x$, $y$ or $alpha$?
    $endgroup$
    – JIM BOY
    Dec 18 '18 at 20:35










  • $begingroup$
    I believe $alpha$ is the variable that is infinitesimal. $x$ and $y$ can just be seen as some coefficients.
    $endgroup$
    – MoonKnight
    Dec 18 '18 at 21:15
















$begingroup$
If $f(x) = f(a) + f'(a)(x - a) + f''(a)/2! (x-a)^2 dots $ is the Taylor series of $f(x)$, then the linearization is just the first two terms: $L(x) = f(a) + f'(a)(x-a)$. Note that this is really just the tangent line to $f(x)$ at $x = a$.
$endgroup$
– JavaMan
Dec 18 '18 at 20:20






$begingroup$
If $f(x) = f(a) + f'(a)(x - a) + f''(a)/2! (x-a)^2 dots $ is the Taylor series of $f(x)$, then the linearization is just the first two terms: $L(x) = f(a) + f'(a)(x-a)$. Note that this is really just the tangent line to $f(x)$ at $x = a$.
$endgroup$
– JavaMan
Dec 18 '18 at 20:20














$begingroup$
I'm still confused, we have three variables, $x$ $y$ and $alpha$. How should I derivate the equation? With respect to $x$, $y$ or $alpha$?
$endgroup$
– JIM BOY
Dec 18 '18 at 20:35




$begingroup$
I'm still confused, we have three variables, $x$ $y$ and $alpha$. How should I derivate the equation? With respect to $x$, $y$ or $alpha$?
$endgroup$
– JIM BOY
Dec 18 '18 at 20:35












$begingroup$
I believe $alpha$ is the variable that is infinitesimal. $x$ and $y$ can just be seen as some coefficients.
$endgroup$
– MoonKnight
Dec 18 '18 at 21:15




$begingroup$
I believe $alpha$ is the variable that is infinitesimal. $x$ and $y$ can just be seen as some coefficients.
$endgroup$
– MoonKnight
Dec 18 '18 at 21:15










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