常用泰勒展开-考研笔记

\begin{align}
\sin x &=x-\frac{x^3}{3!}+\frac{x^5}{5!}-\frac{x^7}{7!}+\frac{x^9}{9!}+o(x^{10}) \\
\cos x&=1-\frac{x^2}{2!}+\frac{x^4}{4!}-\frac{x^6}{6!}+\frac{x^8}{8!}+o(x^9) \\
e^x &=1+ x + \frac{x^2}{2!} + \frac{x^3}{3!} + \frac{x^4}{4!} + \frac{x^5}{5!}+o(x^5) \\
e^{ix} &= 1 + ix -\frac{x^2}{2!} – \frac{ix^3}{3!} +\frac{x^4}{4!}+\frac{ix^5}{5!} …\\
&=\cos x + i\sin x\\
(1-x)^{-1}=\frac{1}{1-x} &=1+x+x^2+x^3+x^4 … \\
(1+x)^{-1}=\frac{1}{1+x} &=1-x+x^2-x^3+x^4 … \\
\ln(1-x)&=-x-\frac{x^2}{2}-\frac{x^3}{3}-\frac{x^4}{4} …\\
\ln(1+x)&=x-\frac{x^2}{2}+\frac{x^3}{3}-\frac{x^4}{4}…\\
\tan x &=x+\frac{x^3}{3}+\frac{2x^5}{15}+o(x^6) \\
\arctan x&=x-\frac{1}{3}x^3+\frac{1}{5}x^5-\frac{1}{7}x^7+\frac{1}{9}x^9+o(x^{10}) \\
\arctan^{‘}x&=1-x^2+x^4-x^6+x^8 … \\
arccot x&=-x+\frac{1}{3}x^3-\frac{1}{5}x^5+\frac{1}{7}x^7-\frac{1}{9}x^9+o(x^{10}) \\

\end{align}

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