- #1
Froskoy
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Homework Statement
Find the first two non-zero terms in the Taylor expansion of [itex]\frac{x}{\sqrt{x^2-a^2}}[/itex] where a is a real constant
Homework Equations
[tex]
f(x)=f(x_0)+f^{\prime}(x_0)(x-x_0)+\frac{f^{\prime\prime}(x_0)}{2!}(x-x_0)^2+...+\frac{f^{(n)}(x_0)}{n!}(x-x_0)^n
[/tex]
The Attempt at a Solution
If a=0 then f(x)=1 (in the case a=0,x=0, use l'Hopital's rule to find the limit of the ratio as [itex]x[/itex] approaches 0 - is this correct?)
then [tex]
f(0)=0
f^{\prime}(0)=\frac{-ai}{a}
f^{\prime\prime}(0)=\frac{-i}{2a^{13}}
[/tex]
Is it OK that there are imaginary terms here? I guess [itex]f(x)[/itex] is imaginary if [itex]a^2>x^2[/itex] anyway?