How to Find the Taylor Polynomial of a Function Composition?

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To find the Taylor polynomial of a composition of functions, such as e^{\cos x}, one can start by expressing each function as its own Taylor series. For instance, near π/2, e^{\cos x} can be expanded using the Taylor series for cos x, which itself can be approximated around that point. The challenge lies in composing these series, and calculating derivatives may simplify the process depending on the desired outcome. A useful method for determining coefficients and constructing the entire series is outlined in the Taylor series documentation. This approach provides a systematic way to derive the polynomial for complex function compositions.
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Is there any nice trick for finding the Taylor polynomial of a composition of 2 functions, both of which can be expressed as taylor polynomials themselves? For example, finding the taylor polynomial for e^{\cos x}. Thanks.
 
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Well, for example, near \pi/2[/tex]<br /> <br /> e^{\cos x}=1+\cos x+ \frac{cos^2 x}{2!}+\frac{\cos^3 x}{3!}+...<br /> <br /> and<br /> <br /> \cos x=-\frac{(x-\pi/2)^2}{2!}+\frac{(x-\pi/2)^4}{4!}-...<br /> <br /> now, the hard part is to compose it, so maybe it&#039;s easier to just calculate the derivative and evaluate, depends on what are you looking for.
 
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